[InstCombine] Restore splat gep support in OptimizePointerDifference() #143906
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
When looking for the common base pointer, support the case where the type changes because the GEP goes from pointer to vector of pointers. This was supported prior to llvm#142958.
llvmbot
added
llvm:instcombine
|
@llvm/pr-subscribers-llvm-transforms Author: Nikita Popov (nikic) ChangesWhen looking for the common base pointer, support the case where the type changes because the GEP goes from pointer to vector of pointers. This was supported prior to #142958. Full diff: https://github.com/llvm/llvm-project/pull/143906.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 86d318967403d..0d91e7d77e4a7 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -2088,8 +2088,6 @@ CommonPointerBase CommonPointerBase::compute(Value *LHS, Value *RHS) {
// Find common base and collect RHS GEPs.
while (true) {
if (Ptrs.contains(RHS)) {
- if (LHS->getType() != RHS->getType())
- return Base;
Base.Ptr = RHS;
break;
}
@@ -2132,12 +2130,15 @@ Value *InstCombinerImpl::OptimizePointerDifference(Value *LHS, Value *RHS,
// TODO: We should probably do this even if there is only one GEP.
bool RewriteGEPs = !Base.LHSGEPs.empty() && !Base.RHSGEPs.empty();
- Type *IdxTy = DL.getIndexType(Base.Ptr->getType());
+ Type *IdxTy = DL.getIndexType(LHS->getType());
auto EmitOffsetFromBase = [&](ArrayRef<GEPOperator *> GEPs,
GEPNoWrapFlags NW) -> Value * {
Value *Sum = nullptr;
for (GEPOperator *GEP : reverse(GEPs)) {
Value *Offset = EmitGEPOffset(GEP, RewriteGEPs);
+ if (Offset->getType() != IdxTy)
+ Offset = Builder.CreateVectorSplat(
+ cast<VectorType>(IdxTy)->getElementCount(), Offset);
if (Sum)
Sum = Builder.CreateAdd(Sum, Offset, "", NW.hasNoUnsignedWrap(),
NW.isInBounds());
diff --git a/llvm/test/Transforms/InstCombine/sub-gep.ll b/llvm/test/Transforms/InstCombine/sub-gep.ll
index 9444fef1887d3..375be8a3d69c3 100644
--- a/llvm/test/Transforms/InstCombine/sub-gep.ll
+++ b/llvm/test/Transforms/InstCombine/sub-gep.ll
@@ -995,3 +995,33 @@ define i64 @multiple_geps_inbounds_nuw(ptr %base, i64 %idx, i64 %idx2) {
%d = sub i64 %i2, %i1
ret i64 %d
}
+
+define <2 x i64> @splat_geps(ptr %base, <2 x i64> %idx1, <2 x i64> %idx2) {
+; CHECK-LABEL: @splat_geps(
+; CHECK-NEXT: [[D:%.*]] = sub nsw <2 x i64> [[IDX2:%.*]], [[IDX1:%.*]]
+; CHECK-NEXT: ret <2 x i64> [[D]]
+;
+ %gep1 = getelementptr inbounds i8, ptr %base, <2 x i64> %idx1
+ %gep2 = getelementptr inbounds i8, ptr %base, <2 x i64> %idx2
+ %gep1.int = ptrtoint <2 x ptr> %gep1 to <2 x i64>
+ %gep2.int = ptrtoint <2 x ptr> %gep2 to <2 x i64>
+ %d = sub <2 x i64> %gep2.int, %gep1.int
+ ret <2 x i64> %d
+}
+
+define <2 x i64> @splat_geps_multiple(ptr %base, i64 %idx0, <2 x i64> %idx1, <2 x i64> %idx2) {
+; CHECK-LABEL: @splat_geps_multiple(
+; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <2 x i64> poison, i64 [[IDX0:%.*]], i64 0
+; CHECK-NEXT: [[DOTSPLAT:%.*]] = shufflevector <2 x i64> [[DOTSPLATINSERT]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[TMP1:%.*]] = add nsw <2 x i64> [[DOTSPLAT]], [[IDX1:%.*]]
+; CHECK-NEXT: [[D:%.*]] = sub nsw <2 x i64> [[IDX2:%.*]], [[TMP1]]
+; CHECK-NEXT: ret <2 x i64> [[D]]
+;
+ %gep0 = getelementptr inbounds i8, ptr %base, i64 %idx0
+ %gep1 = getelementptr inbounds i8, ptr %gep0, <2 x i64> %idx1
+ %gep2 = getelementptr inbounds i8, ptr %base, <2 x i64> %idx2
+ %gep1.int = ptrtoint <2 x ptr> %gep1 to <2 x i64>
+ %gep2.int = ptrtoint <2 x ptr> %gep2 to <2 x i64>
+ %d = sub <2 x i64> %gep2.int, %gep1.int
+ ret <2 x i64> %d
+}
|
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/88/builds/12775 Here is the relevant piece of the build log for the reference |
tomtor
pushed a commit
to tomtor/llvm-project
that referenced
this pull request
Jun 14, 2025
llvm#143906) When looking for the common base pointer, support the case where the type changes because the GEP goes from pointer to vector of pointers. This was supported prior to llvm#142958.
akuhlens
pushed a commit
to akuhlens/llvm-project
that referenced
this pull request
Jun 24, 2025
llvm#143906) When looking for the common base pointer, support the case where the type changes because the GEP goes from pointer to vector of pointers. This was supported prior to llvm#142958.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
When looking for the common base pointer, support the case where the type changes because the GEP goes from pointer to vector of pointers. This was supported prior to #142958.