Interprocedural Register Allocation (IPRA) Analysis

Add an option to enable the analysis of MachineFunction register
usage to extract the list of clobbered registers.

When enabled, the CodeGen order is changed to be bottom up on the Call
Graph.

The analysis is split in two parts, RegUsageInfoCollector is the
MachineFunction Pass that runs post-RA and collect the list of
clobbered registers to produce a register mask.

An immutable pass, RegisterUsageInfo, stores the RegMask produced by
RegUsageInfoCollector, and keep them available. A future tranformation
pass will use this information to update every call-sites after
instruction selection.

Patch by Vivek Pandya <vivekvpandya@gmail.com>

Differential Revision: http://reviews.llvm.org/D20769

llvm-svn: 272403

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
index e7e41d5..3e7261a 100644
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -16,11 +16,13 @@
 
 #include "llvm/Analysis/BasicAliasAnalysis.h"
 #include "llvm/Analysis/CFLAliasAnalysis.h"
+#include "llvm/Analysis/CallGraphSCCPass.h"
 #include "llvm/Analysis/Passes.h"
 #include "llvm/Analysis/ScopedNoAliasAA.h"
 #include "llvm/Analysis/TypeBasedAliasAnalysis.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/RegAllocRegistry.h"
+#include "llvm/CodeGen/RegisterUsageInfo.h"
 #include "llvm/IR/IRPrintingPasses.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Verifier.h"
@@ -112,6 +114,10 @@ static cl::opt<bool> UseCFLAA("use-cfl-aa-in-codegen",
   cl::init(false), cl::Hidden,
   cl::desc("Enable the new, experimental CFL alias analysis in CodeGen"));
 
+cl::opt<bool> UseIPRA("enable-ipra", cl::init(false), cl::Hidden,
+                      cl::desc("Enable interprocedural register allocation "
+                               "to reduce load/store at procedure calls."));
+
 /// Allow standard passes to be disabled by command line options. This supports
 /// simple binary flags that either suppress the pass or do nothing.
 /// i.e. -disable-mypass=false has no effect.
@@ -492,6 +498,10 @@ void TargetPassConfig::addCodeGenPrepare() {
 void TargetPassConfig::addISelPrepare() {
   addPreISel();
 
+  // Force codegen to run according to the callgraph.
+  if (UseIPRA)
+    addPass(new DummyCGSCCPass);
+
   // Add both the safe stack and the stack protection passes: each of them will
   // only protect functions that have corresponding attributes.
   addPass(createSafeStackPass(TM));
@@ -613,6 +623,11 @@ void TargetPassConfig::addMachinePasses() {
 
   addPreEmitPass();
 
+  if (UseIPRA)
+    // Collect register usage information and produce a register mask of
+    // clobbered registers, to be used to optimize call sites.
+    addPass(createRegUsageInfoCollector());
+
   addPass(&FuncletLayoutID, false);
 
   addPass(&StackMapLivenessID, false);