[clang codegen] Emit int TBAA metadata on FP math libcall expf (#96025)

Summary:
Base on the discussion
https://discourse.llvm.org/t/fp-can-we-add-pure-attribute-for-math-library-functions-default/79459,
math libcalls set errno, so it should emit "int" TBAA metadata on FP
libcalls to solve the alias issue.

Note: Only add support for expf in this PR

Fix #86635

Test Plan: 

Reviewers: 

Subscribers: 

Tasks: 

Tags: 


Differential Revision: https://phabricator.intern.facebook.com/D60251692

Author: vfdff

clang/lib/CodeGen/CGBuiltin.cpp

@@ -688,7 +688,34 @@ static RValue emitLibraryCall(CodeGenFunction &CGF, const FunctionDecl *FD,
                               const CallExpr *E, llvm::Constant *calleeValue) {
   CodeGenFunction::CGFPOptionsRAII FPOptsRAII(CGF, E);
   CGCallee callee = CGCallee::forDirect(calleeValue, GlobalDecl(FD));
-  return CGF.EmitCall(E->getCallee()->getType(), callee, E, ReturnValueSlot());
+  RValue Call =
+      CGF.EmitCall(E->getCallee()->getType(), callee, E, ReturnValueSlot());
+
+  // Check the supported intrinsic.
+  if (unsigned BuiltinID = FD->getBuiltinID()) {
+    auto IsErrnoIntrinsic = [&]() -> unsigned {
+      switch (BuiltinID) {
+      case Builtin::BIexpf:
+      case Builtin::BI__builtin_expf:
+      case Builtin::BI__builtin_expf128:
+        return true;
+      }
+      // TODO: support more FP math libcalls
+      return false;
+    }();
+
+    // Restrict to target with errno, for example, MacOS doesn't set errno.
+    if (IsErrnoIntrinsic && CGF.CGM.getLangOpts().MathErrno &&
+        !CGF.Builder.getIsFPConstrained()) {
+      ASTContext &Context = CGF.getContext();
+      // Emit "int" TBAA metadata on FP math libcalls.
+      clang::QualType IntTy = Context.IntTy;
+      TBAAAccessInfo TBAAInfo = CGF.CGM.getTBAAAccessInfo(IntTy);
+      Instruction *Inst = cast<llvm::Instruction>(Call.getScalarVal());
+      CGF.CGM.DecorateInstructionWithTBAA(Inst, TBAAInfo);
+    }
+  }
+  return Call;
 }
 
 /// Emit a call to llvm.{sadd,uadd,ssub,usub,smul,umul}.with.overflow.*

clang/test/CodeGen/math-libcalls-tbaa.cpp

@@ -12,9 +12,8 @@ extern "C" float expf(float);
 // CHECK-NEXT:  [[ENTRY:.*:]]
 // CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i8, ptr [[NUM]], i64 40
 // CHECK-NEXT:    [[TMP0:%.*]] = load float, ptr [[ARRAYIDX]], align 4, !tbaa [[TBAA2:![0-9]+]]
-// CHECK-NEXT:    [[CALL:%.*]] = tail call float @expf(float noundef [[TMP0]]) #[[ATTR2:[0-9]+]]
-// CHECK-NEXT:    [[TMP1:%.*]] = load float, ptr [[ARRAYIDX]], align 4, !tbaa [[TBAA2]]
-// CHECK-NEXT:    [[MUL:%.*]] = fmul float [[CALL]], [[TMP1]]
+// CHECK-NEXT:    [[CALL:%.*]] = tail call float @expf(float noundef [[TMP0]]) #[[ATTR2:[0-9]+]], !tbaa [[TBAA6:![0-9]+]]
+// CHECK-NEXT:    [[MUL:%.*]] = fmul float [[TMP0]], [[CALL]]
 // CHECK-NEXT:    ret float [[MUL]]
 //
 extern "C" float foo (float num[], float r2inv, int n) {
@@ -27,11 +26,15 @@ extern "C" float foo (float num[], float r2inv, int n) {
 // NoNewStructPathTBAA: [[META3]] = !{!"float", [[META4:![0-9]+]], i64 0}
 // NoNewStructPathTBAA: [[META4]] = !{!"omnipotent char", [[META5:![0-9]+]], i64 0}
 // NoNewStructPathTBAA: [[META5]] = !{!"Simple C++ TBAA"}
+// NoNewStructPathTBAA: [[TBAA6]] = !{[[META7:![0-9]+]], [[META7]], i64 0}
+// NoNewStructPathTBAA: [[META7]] = !{!"int", [[META4]], i64 0}
 //.
 // NewStructPathTBAA: [[TBAA2]] = !{[[META3:![0-9]+]], [[META3]], i64 0, i64 4}
 // NewStructPathTBAA: [[META3]] = !{[[META4:![0-9]+]], i64 4, !"float"}
 // NewStructPathTBAA: [[META4]] = !{[[META5:![0-9]+]], i64 1, !"omnipotent char"}
 // NewStructPathTBAA: [[META5]] = !{!"Simple C++ TBAA"}
+// NewStructPathTBAA: [[TBAA6]] = !{[[META7:![0-9]+]], [[META7]], i64 0, i64 4}
+// NewStructPathTBAA: [[META7]] = !{[[META4]], i64 4, !"int"}
 //.
 //// NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
 // NewStructPathTBAA: {{.*}}