[llvm] 1f05778 - InstCombine: Fix insert point for rounding intrinsic -> copysign (#180837)

[via llvm-commits]

Author: Matt Arsenault
Date: 2026-02-11T09:14:12+01:00
New Revision: 1f0577836c32db03b51905bfb78e9dfb1ccd5865

URL: https://github.com/llvm/llvm-project/commit/1f0577836c32db03b51905bfb78e9dfb1ccd5865
DIFF: https://github.com/llvm/llvm-project/commit/1f0577836c32db03b51905bfb78e9dfb1ccd5865.diff

LOG: InstCombine: Fix insert point for rounding intrinsic -> copysign (#180837)

This would use the wrong insert point if reached in a recursive
call.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
    llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-rounding-intrinsics.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index ee66ccc3f7149..43e61adcbaa59 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -3201,6 +3201,9 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Instruction *I,
 
       if ((IID == Intrinsic::trunc || IsRoundNearestOrTrunc) &&
           KnownSrc.isKnownAlways(fcZero | fcSubnormal)) {
+        IRBuilderBase::InsertPointGuard Guard(Builder);
+        Builder.SetInsertPoint(CI);
+
         Value *Copysign = Builder.CreateCopySign(ConstantFP::getZero(VTy),
                                                  CI->getArgOperand(0));
         Copysign->takeName(CI);

diff  --git a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-rounding-intrinsics.ll b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-rounding-intrinsics.ll
index e487b400d87b9..7e2d1bd92fc82 100644
--- a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-rounding-intrinsics.ll
+++ b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-rounding-intrinsics.ll
@@ -494,6 +494,18 @@ define nofpclass(snan) float @source_known_sub_or_zero__trunc(float nofpclass(na
   ret float %result
 }
 
+define nofpclass(snan) float @source_known_sub_or_zero__trunc_insert_point(float nofpclass(nan inf norm) %sub.or.zero) {
+; CHECK-LABEL: define nofpclass(snan) float @source_known_sub_or_zero__trunc_insert_point(
+; CHECK-SAME: float nofpclass(nan inf norm) [[SUB_OR_ZERO:%.*]]) {
+; CHECK-NEXT:    [[RESULT:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[SUB_OR_ZERO]])
+; CHECK-NEXT:    [[BARRIER:%.*]] = call float @llvm.arithmetic.fence.f32(float [[RESULT]])
+; CHECK-NEXT:    ret float [[BARRIER]]
+;
+  %result = call float @llvm.trunc.f32(float %sub.or.zero)
+  %barrier = call float @llvm.arithmetic.fence.f32(float %result)
+  ret float %barrier
+}
+
 define nofpclass(snan) float @source_known_psub_or_pzero__trunc(float nofpclass(nan inf norm nsub nzero) %psub.or.pzero) {
 ; CHECK-LABEL: define nofpclass(snan) float @source_known_psub_or_pzero__trunc(
 ; CHECK-SAME: float nofpclass(nan inf nzero nsub norm) [[PSUB_OR_PZERO:%.*]]) {