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[InstCombine] Propagate invariant.load metadata across unpacked loads #152186

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Merged
merged 7 commits into from
Aug 14, 2025
+50 −0
Merged

[InstCombine] Propagate invariant.load metadata across unpacked loads #152186

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a3d0e64
[InstCombine] Propagate invariant.load metadata across unpacked loads
VedantParanjape Aug 5, 2025
af85146
Merge branch 'main' into invariant-change
VedantParanjape Aug 5, 2025
71d9921
use enums in mdnode
VedantParanjape Aug 6, 2025
9899e69
adjust AAMetadata
VedantParanjape Aug 6, 2025
9955d70
Revert "adjust AAMetadata"
VedantParanjape Aug 13, 2025
2d4e276
addressed review
VedantParanjape Aug 13, 2025
efe732a
Merge branch 'main' into invariant-change
VedantParanjape Aug 14, 2025
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16 changes: 15 additions & 1 deletion llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -718,6 +718,14 @@ static Instruction *combineLoadToOperationType(InstCombinerImpl &IC,
return nullptr;
}

// Check if the aggregate load has a invariant.load metadata
// If aggregate load has invariant.load metadata, add it to the
// unpacked loads as well.
static void copyInvariantLoadMetadata(LoadInst &LI, LoadInst *NewLoad) {
if (MDNode *MD = LI.getMetadata(LLVMContext::MD_invariant_load))
NewLoad->setMetadata(LLVMContext::MD_invariant_load, MD);
}

static Instruction *unpackLoadToAggregate(InstCombinerImpl &IC, LoadInst &LI) {
// FIXME: We could probably with some care handle both volatile and atomic
// stores here but it isn't clear that this is important.
Expand All @@ -737,6 +745,7 @@ static Instruction *unpackLoadToAggregate(InstCombinerImpl &IC, LoadInst &LI) {
LoadInst *NewLoad = IC.combineLoadToNewType(LI, ST->getTypeAtIndex(0U),
".unpack");
NewLoad->setAAMetadata(LI.getAAMetadata());
copyInvariantLoadMetadata(LI, NewLoad);
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Suggested change
copyInvariantLoadMetadata(LI, NewLoad);
NewLI->copyMetadata(LI, LLVMContext::MD_invariant_load);

return IC.replaceInstUsesWith(LI, IC.Builder.CreateInsertValue(
PoisonValue::get(T), NewLoad, 0, Name));
}
Expand All @@ -762,8 +771,13 @@ static Instruction *unpackLoadToAggregate(InstCombinerImpl &IC, LoadInst &LI) {
ST->getElementType(i), Ptr,
commonAlignment(Align, SL->getElementOffset(i).getKnownMinValue()),
Name + ".unpack");
// Adjust AA metadata to new offset and size.
AAMDNodes adjustedAANodes = LI.getAAMetadata().adjustForAccess(
SL->getElementOffset(i),
SL->getElementOffset(i).getKnownMinValue());
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Suggested change
AAMDNodes adjustedAANodes = LI.getAAMetadata().adjustForAccess(
SL->getElementOffset(i),
SL->getElementOffset(i).getKnownMinValue());
TypeSize offset = SL->getElementOffset(i);
AAMDNodes adjustedAANodes = LI.getAAMetadata();
if (offset.isFixed()) {
adjustedAANodes = adjustedAANodes.adjustForAccess(
offset.getFixedValue(),
ST->getElementType(i), DL);
}
else {
adjustedAANodes.TBAA = nullptr;
adjustedAANodes.TBAAStruct = nullptr;
}

For structs with scalable vector elements, the TBAA information is not applicable. You can either zero out or assert here.

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Please file a separate patch for this change. I don't want to block this patch.

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Agreed, this is a separate issue unrelated to this PR.

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Sure, I will upload this as a separate patch.

// Propagate AA metadata. It'll still be valid on the narrowed load.
L->setAAMetadata(LI.getAAMetadata());
L->setAAMetadata(adjustedAANodes);
copyInvariantLoadMetadata(LI, L);
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Suggested change
copyInvariantLoadMetadata(LI, L);
NewLI->copyMetadata(LI, LLVMContext::MD_invariant_load);

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@VedantParanjape VedantParanjape Aug 13, 2025 •
edited
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@dtcxzyw I have fixed these issues, could you please give a lgtm? I will create another PR for adjusting AA metadata.

V = IC.Builder.CreateInsertValue(V, L, i);
}

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46 changes: 46 additions & 0 deletions llvm/test/Transforms/InstCombine/invariant-metadata-propagation.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,46 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -S < %s -passes=instcombine | FileCheck %s

%struct.double2 = type { double, double }
%struct.double1 = type { double }

define %struct.double2 @func1(ptr addrspace(1) %a) {
; CHECK-LABEL: define %struct.double2 @func1(
; CHECK-SAME: ptr addrspace(1) [[A:%.*]]) {
; CHECK-NEXT: [[DOTUNPACK:%.*]] = load double, ptr addrspace(1) [[A]], align 16, !invariant.load [[META0:![0-9]+]]
; CHECK-NEXT: [[TMP1:%.*]] = insertvalue [[STRUCT_DOUBLE2:%.*]] poison, double [[DOTUNPACK]], 0
; CHECK-NEXT: [[DOTELT1:%.*]] = getelementptr inbounds nuw i8, ptr addrspace(1) [[A]], i64 8
; CHECK-NEXT: [[DOTUNPACK2:%.*]] = load double, ptr addrspace(1) [[DOTELT1]], align 8, !invariant.load [[META0]]
; CHECK-NEXT: [[TMP2:%.*]] = insertvalue [[STRUCT_DOUBLE2]] [[TMP1]], double [[DOTUNPACK2]], 1
; CHECK-NEXT: ret [[STRUCT_DOUBLE2]] [[TMP2]]
;
%1 = load %struct.double2, ptr addrspace(1) %a, align 16, !invariant.load !1
ret %struct.double2 %1
}

define %struct.double2 @func2(ptr %a) {
; CHECK-LABEL: define %struct.double2 @func2(
; CHECK-SAME: ptr [[A:%.*]]) {
; CHECK-NEXT: [[DOTUNPACK:%.*]] = load double, ptr [[A]], align 16, !invariant.load [[META0]]
; CHECK-NEXT: [[TMP1:%.*]] = insertvalue [[STRUCT_DOUBLE2:%.*]] poison, double [[DOTUNPACK]], 0
; CHECK-NEXT: [[DOTELT1:%.*]] = getelementptr inbounds nuw i8, ptr [[A]], i64 8
; CHECK-NEXT: [[DOTUNPACK2:%.*]] = load double, ptr [[DOTELT1]], align 8, !invariant.load [[META0]]
; CHECK-NEXT: [[TMP2:%.*]] = insertvalue [[STRUCT_DOUBLE2]] [[TMP1]], double [[DOTUNPACK2]], 1
; CHECK-NEXT: ret [[STRUCT_DOUBLE2]] [[TMP2]]
;
%1 = load %struct.double2, ptr %a, align 16, !invariant.load !1
ret %struct.double2 %1
}

define %struct.double1 @func3(ptr %a) {
; CHECK-LABEL: define %struct.double1 @func3(
; CHECK-SAME: ptr [[A:%.*]]) {
; CHECK-NEXT: [[DOTUNPACK:%.*]] = load double, ptr [[A]], align 16, !invariant.load [[META0]]
; CHECK-NEXT: [[TMP1:%.*]] = insertvalue [[STRUCT_DOUBLE1:%.*]] poison, double [[DOTUNPACK]], 0
; CHECK-NEXT: ret [[STRUCT_DOUBLE1]] [[TMP1]]
;
%1 = load %struct.double1, ptr %a, align 16, !invariant.load !1
ret %struct.double1 %1
}

!1 = !{}
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