[flang] Remove "unsafe-fp-math" attribute support (llvm#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.

Author: paperchalice

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.">,

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

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),

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"{{.*}} }