[clang] 5f2cf3a - [Clang][Preprocessor] Fix inconsistent `FLT_EVAL_METHOD` when compiling vs preprocessing

[Egor Zhdan via cfe-commits]

Author: Egor Zhdan
Date: 2022-06-29T19:36:22+01:00
New Revision: 5f2cf3a21f3aabff85d178a110602ce150914ff7

URL: https://github.com/llvm/llvm-project/commit/5f2cf3a21f3aabff85d178a110602ce150914ff7
DIFF: https://github.com/llvm/llvm-project/commit/5f2cf3a21f3aabff85d178a110602ce150914ff7.diff

LOG: [Clang][Preprocessor] Fix inconsistent `FLT_EVAL_METHOD` when compiling vs preprocessing

When running `clang -E -Ofast` on macOS, the `__FLT_EVAL_METHOD__` macro is `0`, which causes the following typedef to be emitted into the preprocessed source: `typedef float float_t`.

However, when running `clang -c -Ofast`, `__FLT_EVAL_METHOD__` is `-1`, and `typedef long double float_t` is emitted.

This causes build errors for certain projects, which are not reproducible when compiling from preprocessed source.

The issue is that `__FLT_EVAL_METHOD__` is configured in `Sema::Sema` which is not executed when running in `-E` mode.

This change moves that logic into the preprocessor initialization method, which is invoked correctly in `-E` mode.

rdar://96134605
rdar://92748429

Differential Revision: https://reviews.llvm.org/D128814

Added: 
    

Modified: 
    clang/lib/Lex/Preprocessor.cpp
    clang/lib/Sema/Sema.cpp
    clang/test/Preprocessor/flt_eval_macro.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index fcc2d43a34ac9..281f01fb28a40 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -206,6 +206,18 @@ void Preprocessor::Initialize(const TargetInfo &Target,
 
   // Initialize the __FTL_EVAL_METHOD__ macro to the TargetInfo.
   setTUFPEvalMethod(getTargetInfo().getFPEvalMethod());
+
+  if (getLangOpts().getFPEvalMethod() == LangOptions::FEM_UnsetOnCommandLine)
+    // Use setting from TargetInfo.
+    setCurrentFPEvalMethod(SourceLocation(), Target.getFPEvalMethod());
+  else
+    // Set initial value of __FLT_EVAL_METHOD__ from the command line.
+    setCurrentFPEvalMethod(SourceLocation(), getLangOpts().getFPEvalMethod());
+  // When `-ffast-math` option is enabled, it triggers several driver math
+  // options to be enabled. Among those, only one the following two modes
+  // affect the eval-method:  reciprocal or reassociate.
+  if (getLangOpts().AllowFPReassoc || getLangOpts().AllowRecip)
+    setCurrentFPEvalMethod(SourceLocation(), LangOptions::FEM_Indeterminable);
 }
 
 void Preprocessor::InitializeForModelFile() {

diff  --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index ad2cb62a18f0c..e2ec8eec60c33 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -249,21 +249,8 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
   SemaPPCallbackHandler = Callbacks.get();
   PP.addPPCallbacks(std::move(Callbacks));
   SemaPPCallbackHandler->set(*this);
-  if (getLangOpts().getFPEvalMethod() == LangOptions::FEM_UnsetOnCommandLine)
-    // Use setting from TargetInfo.
-    PP.setCurrentFPEvalMethod(SourceLocation(),
-                              ctxt.getTargetInfo().getFPEvalMethod());
-  else
-    // Set initial value of __FLT_EVAL_METHOD__ from the command line.
-    PP.setCurrentFPEvalMethod(SourceLocation(),
-                              getLangOpts().getFPEvalMethod());
+
   CurFPFeatures.setFPEvalMethod(PP.getCurrentFPEvalMethod());
-  // When `-ffast-math` option is enabled, it triggers several driver math
-  // options to be enabled. Among those, only one the following two modes
-  // affect the eval-method:  reciprocal or reassociate.
-  if (getLangOpts().AllowFPReassoc || getLangOpts().AllowRecip)
-    PP.setCurrentFPEvalMethod(SourceLocation(),
-                              LangOptions::FEM_Indeterminable);
 }
 
 // Anchor Sema's type info to this TU.

diff  --git a/clang/test/Preprocessor/flt_eval_macro.cpp b/clang/test/Preprocessor/flt_eval_macro.cpp
index 02829dcd267ec..37c28f21333f9 100644
--- a/clang/test/Preprocessor/flt_eval_macro.cpp
+++ b/clang/test/Preprocessor/flt_eval_macro.cpp
@@ -16,6 +16,9 @@
 // RUN: %clang_cc1 -E -dM -triple=arm64_32-apple-ios -target-feature -sse \
 // RUN:   %s -o - | FileCheck %s  -strict-whitespace
 
+// RUN: %clang_cc1 -E -dM -triple=x86_64-apple-macos13.0 -ffast-math \
+// RUN:   %s -o - | FileCheck %s -check-prefix=CHECK-MINUS-ONE -strict-whitespace
+
 // RUN: %clang_cc1 -E -dM -triple i386-pc-windows -target-cpu pentium4 %s -o - \
 // RUN:   | FileCheck %s  -strict-whitespace
 
@@ -35,7 +38,9 @@
 #define __GLIBC_FLT_EVAL_METHOD 2
 #endif
 
-#if __GLIBC_FLT_EVAL_METHOD == 0 || __GLIBC_FLT_EVAL_METHOD == 16
+#if __GLIBC_FLT_EVAL_METHOD == -1
+#define Name "MinusOne"
+#elif __GLIBC_FLT_EVAL_METHOD == 0 || __GLIBC_FLT_EVAL_METHOD == 16
 #define Name "One"
 #elif __GLIBC_FLT_EVAL_METHOD == 1
 #define Name "Two"
@@ -59,6 +64,7 @@
 
 int foo() {
   // CHECK: #define Name "One"
+  // CHECK-MINUS-ONE: #define Name "MinusOne"
   // EXT: #define Name "Three"
   return Name;
 }