[flang-commits] [flang] 6e9a5c9 - [flang] Remove "unsafe-fp-math" attribute support (#162783)

[via flang-commits]

Author: paperchalice
Date: 2025-10-21T20:24:52+08:00
New Revision: 6e9a5c949391d622943390c207dd73a4406d43b2

URL: https://github.com/llvm/llvm-project/commit/6e9a5c949391d622943390c207dd73a4406d43b2
DIFF: https://github.com/llvm/llvm-project/commit/6e9a5c949391d622943390c207dd73a4406d43b2.diff

LOG: [flang] Remove "unsafe-fp-math" attribute support (#162783)

These global flags block furthur improvements for clang, users should
always use fast-math flags
see also
https://discourse.llvm.org/t/rfc-honor-pragmas-with-ffp-contract-fast/80797
Remove them incrementally, this is the flang part.

Added: 
    

Modified: 
    flang/include/flang/Optimizer/Transforms/Passes.td
    flang/include/flang/Tools/CrossToolHelpers.h
    flang/lib/Optimizer/Transforms/FunctionAttr.cpp
    flang/test/Driver/func-attr-fast-math.f90

Removed: 
    


################################################################################
diff  --git a/flang/include/flang/Optimizer/Transforms/Passes.td b/flang/include/flang/Optimizer/Transforms/Passes.td
index dcff078443473..bb2509b1747d5 100644
--- a/flang/include/flang/Optimizer/Transforms/Passes.td
+++ b/flang/include/flang/Optimizer/Transforms/Passes.td
@@ -436,7 +436,7 @@ def FunctionAttr : Pass<"function-attr", "mlir::func::FuncOp"> {
               "Set the no-signed-zeros-fp-math attribute on functions in the "
               "module.">,
        Option<"unsafeFPMath", "unsafe-fp-math", "bool", /*default=*/"false",
-              "Set the unsafe-fp-math attribute on functions in the module.">,
+              "Set all fast-math flags on instructions in the module.">,
        Option<"reciprocals", "mrecip", "std::string", /*default=*/"",
               "Set the reciprocal-estimates attribute on functions in the "
               "module.">,

diff  --git a/flang/include/flang/Tools/CrossToolHelpers.h b/flang/include/flang/Tools/CrossToolHelpers.h
index 850bd1f0940f7..e964882ef6dac 100644
--- a/flang/include/flang/Tools/CrossToolHelpers.h
+++ b/flang/include/flang/Tools/CrossToolHelpers.h
@@ -128,7 +128,7 @@ struct MLIRToLLVMPassPipelineConfig : public FlangEPCallBacks {
   bool ApproxFuncFPMath = false; ///< Set afn flag for instructions.
   bool NoSignedZerosFPMath =
       false; ///< Set no-signed-zeros-fp-math attribute for functions.
-  bool UnsafeFPMath = false; ///< Set unsafe-fp-math attribute for functions.
+  bool UnsafeFPMath = false; ///< Set all fast-math flags for instructions.
   std::string Reciprocals = ""; ///< Set reciprocal-estimate attribute for
                                 ///< functions.
   std::string PreferVectorWidth = ""; ///< Set prefer-vector-width attribute for

diff  --git a/flang/lib/Optimizer/Transforms/FunctionAttr.cpp b/flang/lib/Optimizer/Transforms/FunctionAttr.cpp
index 9dfe26cbf5899..fea511cc63a37 100644
--- a/flang/lib/Optimizer/Transforms/FunctionAttr.cpp
+++ b/flang/lib/Optimizer/Transforms/FunctionAttr.cpp
@@ -99,10 +99,6 @@ void FunctionAttrPass::runOnOperation() {
     func->setAttr(
         mlir::LLVM::LLVMFuncOp::getNoSignedZerosFpMathAttrName(llvmFuncOpName),
         mlir::BoolAttr::get(context, true));
-  if (unsafeFPMath)
-    func->setAttr(
-        mlir::LLVM::LLVMFuncOp::getUnsafeFpMathAttrName(llvmFuncOpName),
-        mlir::BoolAttr::get(context, true));
   if (!reciprocals.empty())
     func->setAttr(
         mlir::LLVM::LLVMFuncOp::getReciprocalEstimatesAttrName(llvmFuncOpName),

diff  --git a/flang/test/Driver/func-attr-fast-math.f90 b/flang/test/Driver/func-attr-fast-math.f90
index 3b6ce602c5373..3af641ea2db26 100644
--- a/flang/test/Driver/func-attr-fast-math.f90
+++ b/flang/test/Driver/func-attr-fast-math.f90
@@ -11,8 +11,8 @@ end subroutine func
 
 ! CHECK-OFAST-LABEL: define void @func_() local_unnamed_addr
 ! CHECK-OFAST-SAME: #[[ATTRS:[0-9]+]]
-! CHECK-OFAST: attributes #[[ATTRS]] = { {{.*}}"no-infs-fp-math"="true" {{.*}}"no-nans-fp-math"="true" {{.*}}"no-signed-zeros-fp-math"="true" {{.*}}"unsafe-fp-math"="true"{{.*}} }
+! CHECK-OFAST: attributes #[[ATTRS]] = { {{.*}}"no-infs-fp-math"="true" {{.*}}"no-nans-fp-math"="true" {{.*}}"no-signed-zeros-fp-math"="true"{{.*}} }
 
 ! CHECK-FFAST-MATH-LABEL: define void @func_() local_unnamed_addr
 ! CHECK-FFAST-MATH-SAME: #[[ATTRS:[0-9]+]]
-! CHECK-FFAST-MATH: attributes #[[ATTRS]] = { {{.*}}"no-infs-fp-math"="true" {{.*}}"no-nans-fp-math"="true" {{.*}}"no-signed-zeros-fp-math"="true" {{.*}}"unsafe-fp-math"="true"{{.*}} }
+! CHECK-FFAST-MATH: attributes #[[ATTRS]] = { {{.*}}"no-infs-fp-math"="true" {{.*}}"no-nans-fp-math"="true" {{.*}}"no-signed-zeros-fp-math"="true"{{.*}} }