llvm-reduce: Don't remove strictfp

[arsenm]

Summary

The verifier should fail if constrained intrinsics are used in
functions with strictfp, but that patch hasn't been pushed yet.

Ideally we would be able to analyze the function body to see if any
constrained intrinsics were used, but we seem to be missing a utility
function to check for any constrained ops.

[jdoerfert]

LG looks reasonable with the TODO.

[arsenm]

d5b7514c3d298058d2509af5e0093519b1a20662

llvm/test/tools/llvm-reduce/remove-attributes-strictfp.ll

+; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=attributes --test FileCheck --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck --check-prefixes=CHECK,RESULT %s < %t
+
+; Test that invalid reductions aren't produced on strictfp functions.
+
+; CHECK-LABEL: define float @strictfp_intrinsic(float %x, float %y)
+; RESULT-SAME: [[STRICTFP_ONLY:#[0-9]+]] {
+define float @strictfp_intrinsic(float %x, float %y) #0 {
+  %val = call float @llvm.experimental.constrained.fadd.f32(float %x, float %y, metadata !"round.tonearest", metadata !"fpexcept.strict")
+  ret float %val
+}
+
+; CHECK-LABEL: define float @strictfp_callsite(float %x, float %y)
+; RESULT-SAME: [[STRICTFP_ONLY]] {
+; RESULT: call float @extern.func(float %x, float %y) [[STRICTFP_ONLY]]
+define float @strictfp_callsite(float %x, float %y) #0 {
+  %val = call float @extern.func(float %x, float %y) #0
+  ret float %val
+}
+
+; CHECK-LABEL: define float @strictfp_declaration(float %x, float %y)
+; RESULT-SAME: [[STRICTFP_ONLY]] {
+define float @strictfp_declaration(float %x, float %y) #0 {
+  %val = call float @strict.extern.func(float %x, float %y)
+  ret float %val
+}
+
+; CHECK-LABEL: define float @strictfp_no_constrained_ops(float %x, float %y)
+; RESULT-SAME: [[STRICTFP_ONLY]] {
+define float @strictfp_no_constrained_ops(float %x, float %y) #0 {
+  %val = call float @llvm.copysign.f32(float %x, float %y)
+  ret float %val
+}
+
+; CHECK-LABEL: declare float @strict.extern.func(float, float)
+; RESULT-SAME: [[STRICTFP_ONLY]]{{$}}
+declare float @strict.extern.func(float, float) #0
+
+declare float @extern.func(float, float)
+
+declare float @llvm.copysign.f32(float, float) #1
+declare float @llvm.experimental.constrained.fadd.f32(float, float, metadata, metadata) #2
+
+; RESULT: attributes [[STRICTFP_ONLY]] = { strictfp }
+
+attributes #0 = { nounwind strictfp }
+attributes #1 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
+attributes #2 = { nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: readwrite) }

llvm/tools/llvm-reduce/deltas/ReduceAttributes.cpp

void visitAttributeSet(const AttributeSet &AS, AttrBuilder &AttrsToPreserve) {
     for (Attribute A : AS) {
       if (A.isEnumAttribute()) {
         Attribute::AttrKind Kind = A.getKindAsEnum();
         if (Kind == Attribute::NoInline)
           continue;
 
         if (RemoveNoInline && Kind == Attribute::OptimizeNone)
           continue;
+
+        // TODO: Could only remove this if there are no constrained calls in the
+        // function.
+        if (Kind == Attribute::StrictFP) {
+          AttrsToPreserve.addAttribute(A);
+          continue;
+        }
       }
 
       if (O.shouldKeep())
         AttrsToPreserve.addAttribute(A);
     }
   }
 };