[FPEnv] Allow CompoundStmt to keep FP options

This is a recommit of b822efc7404bf09ccfdc1ab7657475026966c3b2,
reverted in dc34d8df4c48b3a8f474360970cae8a58e6c84f0. The commit caused
fails because the test ast-print-fp-pragmas.c did not specify particular
target, and it failed on targets which do not support constrained
intrinsics. The original commit message is below.

AST does not have special nodes for pragmas. Instead a pragma modifies
some state variables of Sema, which in turn results in modified
attributes of AST nodes. This technique applies to floating point
operations as well. Every AST node that can depend on FP options keeps
current set of them.

This technique works well for options like exception behavior or fast
math options. They represent instructions to the compiler how to modify
code generation for the affected nodes. However treatment of FP control
modes has problems with this technique. Modifying FP control mode
(like rounding direction) usually requires operations on hardware, like
writing to control registers. It must be done prior to the first
operation that depends on the control mode. In particular, such
operations are required for implementation of `pragma STDC FENV_ROUND`,
compiler should set up necessary rounding direction at the beginning of
compound statement where the pragma occurs. As there is no representation
for pragmas in AST, the code generation becomes a complicated task in
this case.

To solve this issue FP options are kept inside CompoundStmt. Unlike to FP
options in expressions, these does not affect any operation on FP values,
but only inform the codegen about the FP options that act in the body of
the statement. As all pragmas that modify FP environment may occurs only
at the start of compound statement or at global level, such solution
works for all relevant pragmas. The options are kept as a difference
from the options in the enclosing compound statement or default options,
it helps codegen to set only changed control modes.

Differential Revision: https://reviews.llvm.org/D123952

15 files changed, 150 insertions, 27 deletions

diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 8d930ea..e973011 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -6339,9 +6339,10 @@ ExpectedStmt ASTNodeImporter::VisitCompoundStmt(CompoundStmt *S) {
   if (!ToRBracLocOrErr)
     return ToRBracLocOrErr.takeError();
 
-  return CompoundStmt::Create(
-      Importer.getToContext(), ToStmts,
-      *ToLBracLocOrErr, *ToRBracLocOrErr);
+  FPOptionsOverride FPO =
+      S->hasStoredFPFeatures() ? S->getStoredFPFeatures() : FPOptionsOverride();
+  return CompoundStmt::Create(Importer.getToContext(), ToStmts, FPO,
+                              *ToLBracLocOrErr, *ToRBracLocOrErr);
 }
 
 ExpectedStmt ASTNodeImporter::VisitCaseStmt(CaseStmt *S) {
diff --git a/clang/lib/AST/JSONNodeDumper.cpp b/clang/lib/AST/JSONNodeDumper.cpp
index ae585de..87e4255 100644
--- a/clang/lib/AST/JSONNodeDumper.cpp
+++ b/clang/lib/AST/JSONNodeDumper.cpp
@@ -1692,3 +1692,18 @@ void JSONNodeDumper::visitVerbatimLineComment(
     const comments::VerbatimLineComment *C, const comments::FullComment *) {
   JOS.attribute("text", C->getText());
 }
+
+llvm::json::Object JSONNodeDumper::createFPOptions(FPOptionsOverride FPO) {
+  llvm::json::Object Ret;
+#define OPTION(NAME, TYPE, WIDTH, PREVIOUS)                                    \
+  if (FPO.has##NAME##Override())                                               \
+    Ret.try_emplace(#NAME, static_cast<unsigned>(FPO.get##NAME##Override()));
+#include "clang/Basic/FPOptions.def"
+  return Ret;
+}
+
+void JSONNodeDumper::VisitCompoundStmt(const CompoundStmt *S) {
+  VisitStmt(S);
+  if (S->hasStoredFPFeatures())
+    JOS.attribute("fpoptions", createFPOptions(S->getStoredFPFeatures()));
+}
diff --git a/clang/lib/AST/Stmt.cpp b/clang/lib/AST/Stmt.cpp
index d562717..8eae04d 100644
--- a/clang/lib/AST/Stmt.cpp
+++ b/clang/lib/AST/Stmt.cpp
@@ -361,11 +361,14 @@ int64_t Stmt::getID(const ASTContext &Context) const {
   return Context.getAllocator().identifyKnownAlignedObject<Stmt>(this);
 }
 
-CompoundStmt::CompoundStmt(ArrayRef<Stmt *> Stmts, SourceLocation LB,
-                           SourceLocation RB)
+CompoundStmt::CompoundStmt(ArrayRef<Stmt *> Stmts, FPOptionsOverride FPFeatures,
+                           SourceLocation LB, SourceLocation RB)
     : Stmt(CompoundStmtClass), LBraceLoc(LB), RBraceLoc(RB) {
   CompoundStmtBits.NumStmts = Stmts.size();
+  CompoundStmtBits.HasFPFeatures = FPFeatures.requiresTrailingStorage();
   setStmts(Stmts);
+  if (hasStoredFPFeatures())
+    setStoredFPFeatures(FPFeatures);
 }
 
 void CompoundStmt::setStmts(ArrayRef<Stmt *> Stmts) {
@@ -376,18 +379,23 @@ void CompoundStmt::setStmts(ArrayRef<Stmt *> Stmts) {
 }
 
 CompoundStmt *CompoundStmt::Create(const ASTContext &C, ArrayRef<Stmt *> Stmts,
+                                   FPOptionsOverride FPFeatures,
                                    SourceLocation LB, SourceLocation RB) {
   void *Mem =
-      C.Allocate(totalSizeToAlloc<Stmt *>(Stmts.size()), alignof(CompoundStmt));
-  return new (Mem) CompoundStmt(Stmts, LB, RB);
+      C.Allocate(totalSizeToAlloc<Stmt *, FPOptionsOverride>(
+                     Stmts.size(), FPFeatures.requiresTrailingStorage()),
+                 alignof(CompoundStmt));
+  return new (Mem) CompoundStmt(Stmts, FPFeatures, LB, RB);
 }
 
-CompoundStmt *CompoundStmt::CreateEmpty(const ASTContext &C,
-                                        unsigned NumStmts) {
-  void *Mem =
-      C.Allocate(totalSizeToAlloc<Stmt *>(NumStmts), alignof(CompoundStmt));
+CompoundStmt *CompoundStmt::CreateEmpty(const ASTContext &C, unsigned NumStmts,
+                                        bool HasFPFeatures) {
+  void *Mem = C.Allocate(
+      totalSizeToAlloc<Stmt *, FPOptionsOverride>(NumStmts, HasFPFeatures),
+      alignof(CompoundStmt));
   CompoundStmt *New = new (Mem) CompoundStmt(EmptyShell());
   New->CompoundStmtBits.NumStmts = NumStmts;
+  New->CompoundStmtBits.HasFPFeatures = HasFPFeatures;
   return New;
 }
 
diff --git a/clang/lib/AST/StmtPrinter.cpp b/clang/lib/AST/StmtPrinter.cpp
index 0a959fa..8d77850 100644
--- a/clang/lib/AST/StmtPrinter.cpp
+++ b/clang/lib/AST/StmtPrinter.cpp
@@ -128,6 +128,7 @@ namespace {
     void PrintRawSEHFinallyStmt(SEHFinallyStmt *S);
     void PrintOMPExecutableDirective(OMPExecutableDirective *S,
                                      bool ForceNoStmt = false);
+    void PrintFPPragmas(CompoundStmt *S);
 
     void PrintExpr(Expr *E) {
       if (E)
@@ -174,12 +175,73 @@ namespace {
 /// with no newline after the }.
 void StmtPrinter::PrintRawCompoundStmt(CompoundStmt *Node) {
   OS << "{" << NL;
+  PrintFPPragmas(Node);
   for (auto *I : Node->body())
     PrintStmt(I);
 
   Indent() << "}";
 }
 
+void StmtPrinter::PrintFPPragmas(CompoundStmt *S) {
+  if (!S->hasStoredFPFeatures())
+    return;
+  FPOptionsOverride FPO = S->getStoredFPFeatures();
+  bool FEnvAccess = false;
+  if (FPO.hasAllowFEnvAccessOverride()) {
+    FEnvAccess = FPO.getAllowFEnvAccessOverride();
+    Indent() << "#pragma STDC FENV_ACCESS " << (FEnvAccess ? "ON" : "OFF")
+             << NL;
+  }
+  if (FPO.hasSpecifiedExceptionModeOverride()) {
+    LangOptions::FPExceptionModeKind EM =
+        FPO.getSpecifiedExceptionModeOverride();
+    if (!FEnvAccess || EM != LangOptions::FPE_Strict) {
+      Indent() << "#pragma clang fp exceptions(";
+      switch (FPO.getSpecifiedExceptionModeOverride()) {
+      default:
+        break;
+      case LangOptions::FPE_Ignore:
+        OS << "ignore";
+        break;
+      case LangOptions::FPE_MayTrap:
+        OS << "maytrap";
+        break;
+      case LangOptions::FPE_Strict:
+        OS << "strict";
+        break;
+      }
+      OS << ")\n";
+    }
+  }
+  if (FPO.hasConstRoundingModeOverride()) {
+    LangOptions::RoundingMode RM = FPO.getConstRoundingModeOverride();
+    Indent() << "#pragma STDC FENV_ROUND ";
+    switch (RM) {
+    case llvm::RoundingMode::TowardZero:
+      OS << "FE_TOWARDZERO";
+      break;
+    case llvm::RoundingMode::NearestTiesToEven:
+      OS << "FE_TONEAREST";
+      break;
+    case llvm::RoundingMode::TowardPositive:
+      OS << "FE_UPWARD";
+      break;
+    case llvm::RoundingMode::TowardNegative:
+      OS << "FE_DOWNWARD";
+      break;
+    case llvm::RoundingMode::NearestTiesToAway:
+      OS << "FE_TONEARESTFROMZERO";
+      break;
+    case llvm::RoundingMode::Dynamic:
+      OS << "FE_DYNAMIC";
+      break;
+    default:
+      llvm_unreachable("Invalid rounding mode");
+    }
+    OS << NL;
+  }
+}
+
 void StmtPrinter::PrintRawDecl(Decl *D) {
   D->print(OS, Policy, IndentLevel);
 }
diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
index 7c48fd2..79e9fa6 100644
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -2371,3 +2371,9 @@ void TextNodeDumper::VisitBlockDecl(const BlockDecl *D) {
 void TextNodeDumper::VisitConceptDecl(const ConceptDecl *D) {
   dumpName(D);
 }
+
+void TextNodeDumper::VisitCompoundStmt(const CompoundStmt *S) {
+  VisitStmt(S);
+  if (S->hasStoredFPFeatures())
+    printFPOptions(S->getStoredFPFeatures());
+}
diff --git a/clang/lib/Analysis/BodyFarm.cpp b/clang/lib/Analysis/BodyFarm.cpp
index 8de6927..23d37b8 100644
--- a/clang/lib/Analysis/BodyFarm.cpp
+++ b/clang/lib/Analysis/BodyFarm.cpp
@@ -134,7 +134,8 @@ BinaryOperator *ASTMaker::makeComparison(const Expr *LHS, const Expr *RHS,
 }
 
 CompoundStmt *ASTMaker::makeCompound(ArrayRef<Stmt *> Stmts) {
-  return CompoundStmt::Create(C, Stmts, SourceLocation(), SourceLocation());
+  return CompoundStmt::Create(C, Stmts, FPOptionsOverride(), SourceLocation(),
+                              SourceLocation());
 }
 
 DeclRefExpr *ASTMaker::makeDeclRefExpr(
diff --git a/clang/lib/Basic/LangOptions.cpp b/clang/lib/Basic/LangOptions.cpp
index 0bf410c..753b6bf 100644
--- a/clang/lib/Basic/LangOptions.cpp
+++ b/clang/lib/Basic/LangOptions.cpp
@@ -204,6 +204,15 @@ FPOptions FPOptions::defaultWithoutTrailingStorage(const LangOptions &LO) {
   return result;
 }
 
+FPOptionsOverride FPOptions::getChangesSlow(const FPOptions &Base) const {
+  FPOptions::storage_type OverrideMask = 0;
+#define OPTION(NAME, TYPE, WIDTH, PREVIOUS)                                    \
+  if (get##NAME() != Base.get##NAME())                                         \
+    OverrideMask |= NAME##Mask;
+#include "clang/Basic/FPOptions.def"
+  return FPOptionsOverride(*this, OverrideMask);
+}
+
 LLVM_DUMP_METHOD void FPOptions::dump() {
 #define OPTION(NAME, TYPE, WIDTH, PREVIOUS)                                    \
   llvm::errs() << "\n " #NAME " " << get##NAME();
diff --git a/clang/lib/CodeGen/CGCoroutine.cpp b/clang/lib/CodeGen/CGCoroutine.cpp
index 4216ca1..594c7d4 100644
--- a/clang/lib/CodeGen/CGCoroutine.cpp
+++ b/clang/lib/CodeGen/CGCoroutine.cpp
@@ -238,8 +238,8 @@ static LValueOrRValue emitSuspendExpression(CodeGenFunction &CGF, CGCoroData &Co
     auto Loc = S.getResumeExpr()->getExprLoc();
     auto *Catch = new (CGF.getContext())
         CXXCatchStmt(Loc, /*exDecl=*/nullptr, Coro.ExceptionHandler);
-    auto *TryBody =
-        CompoundStmt::Create(CGF.getContext(), S.getResumeExpr(), Loc, Loc);
+    auto *TryBody = CompoundStmt::Create(CGF.getContext(), S.getResumeExpr(),
+                                         FPOptionsOverride(), Loc, Loc);
     TryStmt = CXXTryStmt::Create(CGF.getContext(), Loc, TryBody, Catch);
     CGF.EnterCXXTryStmt(*TryStmt);
   }
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index e2ec8ee..326010d 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -2219,7 +2219,8 @@ operator()(sema::FunctionScopeInfo *Scope) const {
 }
 
 void Sema::PushCompoundScope(bool IsStmtExpr) {
-  getCurFunction()->CompoundScopes.push_back(CompoundScopeInfo(IsStmtExpr));
+  getCurFunction()->CompoundScopes.push_back(
+      CompoundScopeInfo(IsStmtExpr, getCurFPFeatures()));
 }
 
 void Sema::PopCompoundScope() {
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index a70c857..221cbd1 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -15353,8 +15353,8 @@ void Sema::DefineImplicitLambdaToFunctionPointerConversion(
                                        VK_LValue, Conv->getLocation());
   assert(FunctionRef && "Can't refer to __invoke function?");
   Stmt *Return = BuildReturnStmt(Conv->getLocation(), FunctionRef).get();
-  Conv->setBody(CompoundStmt::Create(Context, Return, Conv->getLocation(),
-                                     Conv->getLocation()));
+  Conv->setBody(CompoundStmt::Create(Context, Return, FPOptionsOverride(),
+                                     Conv->getLocation(), Conv->getLocation()));
   Conv->markUsed(Context);
   Conv->setReferenced();
 
@@ -15408,8 +15408,8 @@ void Sema::DefineImplicitLambdaToBlockPointerConversion(
 
   // Set the body of the conversion function.
   Stmt *ReturnS = Return.get();
-  Conv->setBody(CompoundStmt::Create(Context, ReturnS, Conv->getLocation(),
-                                     Conv->getLocation()));
+  Conv->setBody(CompoundStmt::Create(Context, ReturnS, FPOptionsOverride(),
+                                     Conv->getLocation(), Conv->getLocation()));
   Conv->markUsed(Context);
 
   // We're done; notify the mutation listener, if any.
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index fadcdc4..0d73fcf 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -7295,8 +7295,9 @@ Stmt *Sema::MaybeCreateStmtWithCleanups(Stmt *SubStmt) {
   // a StmtExpr; currently this is only used for asm statements.
   // This is hacky, either create a new CXXStmtWithTemporaries statement or
   // a new AsmStmtWithTemporaries.
-  CompoundStmt *CompStmt = CompoundStmt::Create(
-      Context, SubStmt, SourceLocation(), SourceLocation());
+  CompoundStmt *CompStmt =
+      CompoundStmt::Create(Context, SubStmt, FPOptionsOverride(),
+                           SourceLocation(), SourceLocation());
   Expr *E = new (Context)
       StmtExpr(CompStmt, Context.VoidTy, SourceLocation(), SourceLocation(),
                /*FIXME TemplateDepth=*/0);
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 117fec4..6f50196 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -14681,8 +14681,8 @@ StmtResult Sema::ActOnOpenMPTileDirective(ArrayRef<OMPClause *> Clauses,
     SmallVector<Stmt *, 4> BodyParts;
     BodyParts.append(LoopHelper.Updates.begin(), LoopHelper.Updates.end());
     BodyParts.push_back(Inner);
-    Inner = CompoundStmt::Create(Context, BodyParts, Inner->getBeginLoc(),
-                                 Inner->getEndLoc());
+    Inner = CompoundStmt::Create(Context, BodyParts, FPOptionsOverride(),
+                                 Inner->getBeginLoc(), Inner->getEndLoc());
     Inner = new (Context)
         ForStmt(Context, InitStmt.get(), CondExpr.get(), nullptr,
                 IncrStmt.get(), Inner, LoopHelper.Init->getBeginLoc(),
@@ -14956,8 +14956,9 @@ StmtResult Sema::ActOnOpenMPUnrollDirective(ArrayRef<OMPClause *> Clauses,
   SmallVector<Stmt *> InnerBodyStmts;
   InnerBodyStmts.append(LoopHelper.Updates.begin(), LoopHelper.Updates.end());
   InnerBodyStmts.push_back(Body);
-  CompoundStmt *InnerBody = CompoundStmt::Create(
-      Context, InnerBodyStmts, Body->getBeginLoc(), Body->getEndLoc());
+  CompoundStmt *InnerBody =
+      CompoundStmt::Create(Context, InnerBodyStmts, FPOptionsOverride(),
+                           Body->getBeginLoc(), Body->getEndLoc());
   ForStmt *InnerFor = new (Context)
       ForStmt(Context, InnerInit.get(), InnerCond.get(), nullptr,
               InnerIncr.get(), InnerBody, LoopHelper.Init->getBeginLoc(),
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 82831a4..f25694c 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -442,7 +442,16 @@ StmtResult Sema::ActOnCompoundStmt(SourceLocation L, SourceLocation R,
       DiagnoseEmptyLoopBody(Elts[i], Elts[i + 1]);
   }
 
-  return CompoundStmt::Create(Context, Elts, L, R);
+  // Calculate difference between FP options in this compound statement and in
+  // the enclosing one. If this is a function body, take the difference against
+  // default options. In this case the difference will indicate options that are
+  // changed upon entry to the statement.
+  FPOptions FPO = (getCurFunction()->CompoundScopes.size() == 1)
+                      ? FPOptions(getLangOpts())
+                      : getCurCompoundScope().InitialFPFeatures;
+  FPOptionsOverride FPDiff = getCurFPFeatures().getChangesFrom(FPO);
+
+  return CompoundStmt::Create(Context, Elts, FPDiff, L, R);
 }
 
 ExprResult
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index 0b715bc1..e0ae019 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -152,9 +152,14 @@ void ASTStmtReader::VisitCompoundStmt(CompoundStmt *S) {
   VisitStmt(S);
   SmallVector<Stmt *, 16> Stmts;
   unsigned NumStmts = Record.readInt();
+  unsigned HasFPFeatures = Record.readInt();
+  assert(S->hasStoredFPFeatures() == HasFPFeatures);
   while (NumStmts--)
     Stmts.push_back(Record.readSubStmt());
   S->setStmts(Stmts);
+  if (HasFPFeatures)
+    S->setStoredFPFeatures(
+        FPOptionsOverride::getFromOpaqueInt(Record.readInt()));
   S->LBraceLoc = readSourceLocation();
   S->RBraceLoc = readSourceLocation();
 }
@@ -2768,7 +2773,8 @@ Stmt *ASTReader::ReadStmtFromStream(ModuleFile &F) {
 
     case STMT_COMPOUND:
       S = CompoundStmt::CreateEmpty(
-          Context, /*NumStmts=*/Record[ASTStmtReader::NumStmtFields]);
+          Context, /*NumStmts=*/Record[ASTStmtReader::NumStmtFields],
+          /*HasFPFeatures=*/Record[ASTStmtReader::NumStmtFields + 1]);
       break;
 
     case STMT_CASE:
diff --git a/clang/lib/Serialization/ASTWriterStmt.cpp b/clang/lib/Serialization/ASTWriterStmt.cpp
index f3e0868..5e5a86e 100644
--- a/clang/lib/Serialization/ASTWriterStmt.cpp
+++ b/clang/lib/Serialization/ASTWriterStmt.cpp
@@ -81,8 +81,11 @@ void ASTStmtWriter::VisitNullStmt(NullStmt *S) {
 void ASTStmtWriter::VisitCompoundStmt(CompoundStmt *S) {
   VisitStmt(S);
   Record.push_back(S->size());
+  Record.push_back(S->hasStoredFPFeatures());
   for (auto *CS : S->body())
     Record.AddStmt(CS);
+  if (S->hasStoredFPFeatures())
+    Record.push_back(S->getStoredFPFeatures().getAsOpaqueInt());
   Record.AddSourceLocation(S->getLBracLoc());
   Record.AddSourceLocation(S->getRBracLoc());
   Code = serialization::STMT_COMPOUND;