[llvm] 1528ddb - [ConstantFolding][SVE] Do not fold fcmp of denormal without known mode. (#150614)

[via llvm-commits]

Author: Paul Walker
Date: 2025-07-29T12:37:59+01:00
New Revision: 1528ddbe76acbd80e3da44b3f248fc566d6ab40b

URL: https://github.com/llvm/llvm-project/commit/1528ddbe76acbd80e3da44b3f248fc566d6ab40b
DIFF: https://github.com/llvm/llvm-project/commit/1528ddbe76acbd80e3da44b3f248fc566d6ab40b.diff

LOG: [ConstantFolding][SVE] Do not fold fcmp of denormal without known mode. (#150614)

This is a follow on to
https://github.com/llvm/llvm-project/pull/115407 that introduced code
which bypasses the splat handling for scalable vectors. To maintain
existing tests I have moved the early return until after the splat
handling so all vector types are treated equally.

Added: 
    

Modified: 
    llvm/lib/Analysis/ConstantFolding.cpp
    llvm/test/Transforms/SCCP/no-fold-fcmp-dynamic-denormal-mode-issue114947.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 759c553111d06..7341dade1619d 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1373,7 +1373,7 @@ Constant *llvm::FlushFPConstant(Constant *Operand, const Instruction *Inst,
   if (ConstantFP *CFP = dyn_cast<ConstantFP>(Operand))
     return flushDenormalConstantFP(CFP, Inst, IsOutput);
 
-  if (isa<ConstantAggregateZero, UndefValue, ConstantExpr>(Operand))
+  if (isa<ConstantAggregateZero, UndefValue>(Operand))
     return Operand;
 
   Type *Ty = Operand->getType();
@@ -1389,6 +1389,9 @@ Constant *llvm::FlushFPConstant(Constant *Operand, const Instruction *Inst,
     Ty = VecTy->getElementType();
   }
 
+  if (isa<ConstantExpr>(Operand))
+    return Operand;
+
   if (const auto *CV = dyn_cast<ConstantVector>(Operand)) {
     SmallVector<Constant *, 16> NewElts;
     for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {

diff  --git a/llvm/test/Transforms/SCCP/no-fold-fcmp-dynamic-denormal-mode-issue114947.ll b/llvm/test/Transforms/SCCP/no-fold-fcmp-dynamic-denormal-mode-issue114947.ll
index 1eb5417d5ffdf..285122d104c7e 100644
--- a/llvm/test/Transforms/SCCP/no-fold-fcmp-dynamic-denormal-mode-issue114947.ll
+++ b/llvm/test/Transforms/SCCP/no-fold-fcmp-dynamic-denormal-mode-issue114947.ll
@@ -106,10 +106,11 @@ define <vscale x 2 x i1> @fold_fcmp_nondenormal_double_ieee_dynamic_scalable_vec
   ret <vscale x 2 x i1> %cmp
 }
 
-define <vscale x 2 x i1> @no_fold_fcmp_denormal_double_ieee_dynamic_scalaable_vector_splat() #0 {
-; CHECK-LABEL: define <vscale x 2 x i1> @no_fold_fcmp_denormal_double_ieee_dynamic_scalaable_vector_splat(
+define <vscale x 2 x i1> @no_fold_fcmp_denormal_double_ieee_dynamic_scalable_vector_splat() #0 {
+; CHECK-LABEL: define <vscale x 2 x i1> @no_fold_fcmp_denormal_double_ieee_dynamic_scalable_vector_splat(
 ; CHECK-SAME: ) #[[ATTR0]] {
-; CHECK-NEXT:    ret <vscale x 2 x i1> splat (i1 true)
+; CHECK-NEXT:    [[CMP:%.*]] = fcmp une <vscale x 2 x double> splat (double 0x8000000000000), zeroinitializer
+; CHECK-NEXT:    ret <vscale x 2 x i1> [[CMP]]
 ;
   %cmp = fcmp une <vscale x 2 x double> splat (double 0x8000000000000), zeroinitializer
   ret <vscale x 2 x i1> %cmp