[llvm] [ConstandFolding][SVE] Do not fold fcmp of denormal without known mode. (PR #150614)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm created https://github.com/llvm/llvm-project/pull/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.

>From 084924d25a7e3b59121ebaa330c19f8ee5d4251e Mon Sep 17 00:00:00 2001
From: Paul Walker <paul.walker at arm.com>
Date: Fri, 25 Jul 2025 12:59:21 +0000
Subject: [PATCH] [ConstandFolding][SVE] Do not fold fcmp of denormal without
 known mode.

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.
---
 llvm/lib/Analysis/ConstantFolding.cpp                        | 5 ++++-
 .../SCCP/no-fold-fcmp-dynamic-denormal-mode-issue114947.ll   | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index ec78386def24f..acccd0988693e 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1374,7 +1374,7 @@ 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();
@@ -1390,6 +1390,9 @@ 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..525bf31824f9a 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
@@ -109,7 +109,8 @@ define <vscale x 2 x i1> @fold_fcmp_nondenormal_double_ieee_dynamic_scalable_vec
 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(
 ; 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