[attrs] Extract the pure inference of function attributes into

a standalone pass.

There is no call graph or even interesting analysis for this part of
function attributes -- it is literally inferring attributes based on the
target library identification. As such, we can do it using a much
simpler module pass that just walks the declarations. This can also
happen much earlier in the pass pipeline which has benefits for any
number of other passes.

In the process, I've cleaned up one particular aspect of the logic which
was necessary in order to separate the two passes cleanly. It now counts
inferred attributes independently rather than just counting all the
inferred attributes as one, and the counts are more clearly explained.

The two test cases we had for this code path are both ... woefully
inadequate and copies of each other. I've kept the superset test and
updated it. We need more testing here, but I had to pick somewhere to
stop fixing everything broken I saw here.

Differential Revision: http://reviews.llvm.org/D15676

llvm-svn: 256466

1 files changed, 937 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/IPO/InferFunctionAttrs.cpp b/llvm/lib/Transforms/IPO/InferFunctionAttrs.cpp
new file mode 100644
index 0000000..d02c861
--- /dev/null
+++ b/llvm/lib/Transforms/IPO/InferFunctionAttrs.cpp
@@ -0,0 +1,937 @@
+//===- InferFunctionAttrs.cpp - Infer implicit function attributes --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/IPO/InferFunctionAttrs.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "inferattrs"
+
+STATISTIC(NumReadNone, "Number of functions inferred as readnone");
+STATISTIC(NumReadOnly, "Number of functions inferred as readonly");
+STATISTIC(NumNoUnwind, "Number of functions inferred as nounwind");
+STATISTIC(NumNoCapture, "Number of arguments inferred as nocapture");
+STATISTIC(NumReadOnlyArg, "Number of arguments inferred as readonly");
+STATISTIC(NumNoAlias, "Number of function returns inferred as noalias");
+
+static bool setDoesNotAccessMemory(Function &F) {
+  if (F.doesNotAccessMemory())
+    return false;
+  F.setDoesNotAccessMemory();
+  ++NumReadNone;
+  return true;
+}
+
+static bool setOnlyReadsMemory(Function &F) {
+  if (F.onlyReadsMemory())
+    return false;
+  F.setOnlyReadsMemory();
+  ++NumReadOnly;
+  return true;
+}
+
+static bool setDoesNotThrow(Function &F) {
+  if (F.doesNotThrow())
+    return false;
+  F.setDoesNotThrow();
+  ++NumNoUnwind;
+  return true;
+}
+
+static bool setDoesNotCapture(Function &F, unsigned n) {
+  if (F.doesNotCapture(n))
+    return false;
+  F.setDoesNotCapture(n);
+  ++NumNoCapture;
+  return true;
+}
+
+static bool setOnlyReadsMemory(Function &F, unsigned n) {
+  if (F.onlyReadsMemory(n))
+    return false;
+  F.setOnlyReadsMemory(n);
+  ++NumReadOnlyArg;
+  return true;
+}
+
+static bool setDoesNotAlias(Function &F, unsigned n) {
+  if (F.doesNotAlias(n))
+    return false;
+  F.setDoesNotAlias(n);
+  ++NumNoAlias;
+  return true;
+}
+
+/// Analyze the name and prototype of the given function and set any applicable
+/// attributes.
+///
+/// Returns true if any attributes were set and false otherwise.
+static bool inferPrototypeAttributes(Function &F,
+                                     const TargetLibraryInfo &TLI) {
+  if (F.hasFnAttribute(Attribute::OptimizeNone))
+    return false;
+
+  FunctionType *FTy = F.getFunctionType();
+  LibFunc::Func TheLibFunc;
+  if (!(TLI.getLibFunc(F.getName(), TheLibFunc) && TLI.has(TheLibFunc)))
+    return false;
+
+  bool Changed = false;
+
+  switch (TheLibFunc) {
+  case LibFunc::strlen:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setOnlyReadsMemory(F);
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::strchr:
+  case LibFunc::strrchr:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isIntegerTy())
+      return false;
+    Changed |= setOnlyReadsMemory(F);
+    Changed |= setDoesNotThrow(F);
+    return Changed;
+  case LibFunc::strtol:
+  case LibFunc::strtod:
+  case LibFunc::strtof:
+  case LibFunc::strtoul:
+  case LibFunc::strtoll:
+  case LibFunc::strtold:
+  case LibFunc::strtoull:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::strcpy:
+  case LibFunc::stpcpy:
+  case LibFunc::strcat:
+  case LibFunc::strncat:
+  case LibFunc::strncpy:
+  case LibFunc::stpncpy:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::strxfrm:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::strcmp:      // 0,1
+  case LibFunc::strspn:      // 0,1
+  case LibFunc::strncmp:     // 0,1
+  case LibFunc::strcspn:     // 0,1
+  case LibFunc::strcoll:     // 0,1
+  case LibFunc::strcasecmp:  // 0,1
+  case LibFunc::strncasecmp: //
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setOnlyReadsMemory(F);
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::strstr:
+  case LibFunc::strpbrk:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setOnlyReadsMemory(F);
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::strtok:
+  case LibFunc::strtok_r:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::scanf:
+    if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::setbuf:
+  case LibFunc::setvbuf:
+    if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::strdup:
+  case LibFunc::strndup:
+    if (FTy->getNumParams() < 1 || !FTy->getReturnType()->isPointerTy() ||
+        !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::stat:
+  case LibFunc::statvfs:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::sscanf:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::sprintf:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::snprintf:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(2)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 3);
+    Changed |= setOnlyReadsMemory(F, 3);
+    return Changed;
+  case LibFunc::setitimer:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy() ||
+        !FTy->getParamType(2)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setDoesNotCapture(F, 3);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::system:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    // May throw; "system" is a valid pthread cancellation point.
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::malloc:
+    if (FTy->getNumParams() != 1 || !FTy->getReturnType()->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    return Changed;
+  case LibFunc::memcmp:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setOnlyReadsMemory(F);
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::memchr:
+  case LibFunc::memrchr:
+    if (FTy->getNumParams() != 3)
+      return false;
+    Changed |= setOnlyReadsMemory(F);
+    Changed |= setDoesNotThrow(F);
+    return Changed;
+  case LibFunc::modf:
+  case LibFunc::modff:
+  case LibFunc::modfl:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::memcpy:
+  case LibFunc::memccpy:
+  case LibFunc::memmove:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::memalign:
+    if (!FTy->getReturnType()->isPointerTy())
+      return false;
+    Changed |= setDoesNotAlias(F, 0);
+    return Changed;
+  case LibFunc::mkdir:
+    if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::mktime:
+    if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::realloc:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getReturnType()->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::read:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    // May throw; "read" is a valid pthread cancellation point.
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::rewind:
+    if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::rmdir:
+  case LibFunc::remove:
+  case LibFunc::realpath:
+    if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::rename:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::readlink:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::write:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    // May throw; "write" is a valid pthread cancellation point.
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::bcopy:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::bcmp:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setOnlyReadsMemory(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::bzero:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::calloc:
+    if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    return Changed;
+  case LibFunc::chmod:
+  case LibFunc::chown:
+    if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::ctermid:
+  case LibFunc::clearerr:
+  case LibFunc::closedir:
+    if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::atoi:
+  case LibFunc::atol:
+  case LibFunc::atof:
+  case LibFunc::atoll:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setOnlyReadsMemory(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::access:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::fopen:
+    if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy() ||
+        !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::fdopen:
+    if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::feof:
+  case LibFunc::free:
+  case LibFunc::fseek:
+  case LibFunc::ftell:
+  case LibFunc::fgetc:
+  case LibFunc::fseeko:
+  case LibFunc::ftello:
+  case LibFunc::fileno:
+  case LibFunc::fflush:
+  case LibFunc::fclose:
+  case LibFunc::fsetpos:
+  case LibFunc::flockfile:
+  case LibFunc::funlockfile:
+  case LibFunc::ftrylockfile:
+    if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::ferror:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F);
+    return Changed;
+  case LibFunc::fputc:
+  case LibFunc::fstat:
+  case LibFunc::frexp:
+  case LibFunc::frexpf:
+  case LibFunc::frexpl:
+  case LibFunc::fstatvfs:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::fgets:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(2)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 3);
+    return Changed;
+  case LibFunc::fread:
+    if (FTy->getNumParams() != 4 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(3)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 4);
+    return Changed;
+  case LibFunc::fwrite:
+    if (FTy->getNumParams() != 4 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(3)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 4);
+    return Changed;
+  case LibFunc::fputs:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::fscanf:
+  case LibFunc::fprintf:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::fgetpos:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::getc:
+  case LibFunc::getlogin_r:
+  case LibFunc::getc_unlocked:
+    if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::getenv:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setOnlyReadsMemory(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::gets:
+  case LibFunc::getchar:
+    Changed |= setDoesNotThrow(F);
+    return Changed;
+  case LibFunc::getitimer:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::getpwnam:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::ungetc:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::uname:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::unlink:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::unsetenv:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::utime:
+  case LibFunc::utimes:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::putc:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::puts:
+  case LibFunc::printf:
+  case LibFunc::perror:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::pread:
+    if (FTy->getNumParams() != 4 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    // May throw; "pread" is a valid pthread cancellation point.
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::pwrite:
+    if (FTy->getNumParams() != 4 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    // May throw; "pwrite" is a valid pthread cancellation point.
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::putchar:
+    Changed |= setDoesNotThrow(F);
+    return Changed;
+  case LibFunc::popen:
+    if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy() ||
+        !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::pclose:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::vscanf:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::vsscanf:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy() ||
+        !FTy->getParamType(2)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::vfscanf:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy() ||
+        !FTy->getParamType(2)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::valloc:
+    if (!FTy->getReturnType()->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    return Changed;
+  case LibFunc::vprintf:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::vfprintf:
+  case LibFunc::vsprintf:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::vsnprintf:
+    if (FTy->getNumParams() != 4 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(2)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 3);
+    Changed |= setOnlyReadsMemory(F, 3);
+    return Changed;
+  case LibFunc::open:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    // May throw; "open" is a valid pthread cancellation point.
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::opendir:
+    if (FTy->getNumParams() != 1 || !FTy->getReturnType()->isPointerTy() ||
+        !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::tmpfile:
+    if (!FTy->getReturnType()->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    return Changed;
+  case LibFunc::times:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::htonl:
+  case LibFunc::htons:
+  case LibFunc::ntohl:
+  case LibFunc::ntohs:
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAccessMemory(F);
+    return Changed;
+  case LibFunc::lstat:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::lchown:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::qsort:
+    if (FTy->getNumParams() != 4 || !FTy->getParamType(3)->isPointerTy())
+      return false;
+    // May throw; places call through function pointer.
+    Changed |= setDoesNotCapture(F, 4);
+    return Changed;
+  case LibFunc::dunder_strdup:
+  case LibFunc::dunder_strndup:
+    if (FTy->getNumParams() < 1 || !FTy->getReturnType()->isPointerTy() ||
+        !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::dunder_strtok_r:
+    if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::under_IO_getc:
+    if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::under_IO_putc:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::dunder_isoc99_scanf:
+    if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::stat64:
+  case LibFunc::lstat64:
+  case LibFunc::statvfs64:
+    if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::dunder_isoc99_sscanf:
+    if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::fopen64:
+    if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy() ||
+        !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    Changed |= setOnlyReadsMemory(F, 1);
+    Changed |= setOnlyReadsMemory(F, 2);
+    return Changed;
+  case LibFunc::fseeko64:
+  case LibFunc::ftello64:
+    if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    return Changed;
+  case LibFunc::tmpfile64:
+    if (!FTy->getReturnType()->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotAlias(F, 0);
+    return Changed;
+  case LibFunc::fstat64:
+  case LibFunc::fstatvfs64:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
+      return false;
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+  case LibFunc::open64:
+    if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy())
+      return false;
+    // May throw; "open" is a valid pthread cancellation point.
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setOnlyReadsMemory(F, 1);
+    return Changed;
+  case LibFunc::gettimeofday:
+    if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
+        !FTy->getParamType(1)->isPointerTy())
+      return false;
+    // Currently some platforms have the restrict keyword on the arguments to
+    // gettimeofday. To be conservative, do not add noalias to gettimeofday's
+    // arguments.
+    Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCapture(F, 1);
+    Changed |= setDoesNotCapture(F, 2);
+    return Changed;
+
+  default:
+    // FIXME: It'd be really nice to cover all the library functions we're
+    // aware of here.
+    return false;
+  }
+}
+
+static bool inferAllPrototypeAttributes(Module &M,
+                                        const TargetLibraryInfo &TLI) {
+  bool Changed = false;
+
+  for (Function &F : M.functions())
+    // We only infer things using the prototype if the definition isn't around
+    // to analyze directly.
+    if (F.isDeclaration())
+      Changed |= inferPrototypeAttributes(F, TLI);
+
+  return Changed;
+}
+
+PreservedAnalyses InferFunctionAttrsPass::run(Module &M,
+                                              AnalysisManager<Module> *AM) {
+  auto &TLI = AM->getResult<TargetLibraryAnalysis>(M);
+
+  if (!inferAllPrototypeAttributes(M, TLI))
+    // If we didn't infer anything, preserve all analyses.
+    return PreservedAnalyses::all();
+
+  // Otherwise, we may have changed fundamental function attributes, so clear
+  // out all the passes.
+  return PreservedAnalyses::none();
+}
+
+namespace {
+struct InferFunctionAttrsLegacyPass : public ModulePass {
+  static char ID; // Pass identification, replacement for typeid
+  InferFunctionAttrsLegacyPass() : ModulePass(ID) {
+    initializeInferFunctionAttrsLegacyPassPass(
+        *PassRegistry::getPassRegistry());
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addRequired<TargetLibraryInfoWrapperPass>();
+  }
+
+  bool runOnModule(Module &M) override {
+    auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+    return inferAllPrototypeAttributes(M, TLI);
+  }
+};
+}
+
+char InferFunctionAttrsLegacyPass::ID = 0;
+INITIALIZE_PASS_BEGIN(InferFunctionAttrsLegacyPass, "inferattrs",
+                      "Infer set function attributes", false, false)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_END(InferFunctionAttrsLegacyPass, "inferattrs",
+                    "Infer set function attributes", false, false)
+
+Pass *llvm::createInferFunctionAttrsLegacyPass() {
+  return new InferFunctionAttrsLegacyPass();
+}