[llvm] [InstCombine] Fold align assume into load's !align metadata if possible. (PR #108958)
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 17 05:05:29 PDT 2024
https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/108958
>From 24f656e089a747dce9a38992c3a9c98e3c087293 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Tue, 17 Sep 2024 10:50:09 +0100
Subject: [PATCH 1/3] [InstCombine] Fold align assume into load's !align
metadata if possible.
If an alignment assumption is valid in the context of a corresponding
load of the pointer the assumption applies to, the assumption can be
replaced !align metadata on the load.
The benefits of folding it into !align are that existing code makes
better use of !align and it allows removing the now-redundant call
instructions.
---
.../InstCombine/InstCombineCalls.cpp | 25 ++++++++++++++++---
.../Transforms/InstCombine/assume-align.ll | 7 +++---
2 files changed, 25 insertions(+), 7 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 61011d55227e7b..596de10e20b6de 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3076,12 +3076,13 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
// TODO: apply range metadata for range check patterns?
}
- // Separate storage assumptions apply to the underlying allocations, not any
- // particular pointer within them. When evaluating the hints for AA purposes
- // we getUnderlyingObject them; by precomputing the answers here we can
- // avoid having to do so repeatedly there.
for (unsigned Idx = 0; Idx < II->getNumOperandBundles(); Idx++) {
OperandBundleUse OBU = II->getOperandBundleAt(Idx);
+
+ // Separate storage assumptions apply to the underlying allocations, not any
+ // particular pointer within them. When evaluating the hints for AA purposes
+ // we getUnderlyingObject them; by precomputing the answers here we can
+ // avoid having to do so repeatedly there.
if (OBU.getTagName() == "separate_storage") {
assert(OBU.Inputs.size() == 2);
auto MaybeSimplifyHint = [&](const Use &U) {
@@ -3095,6 +3096,22 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
MaybeSimplifyHint(OBU.Inputs[0]);
MaybeSimplifyHint(OBU.Inputs[1]);
}
+
+ // Try to fold alignment assumption into a load's !align metadata, if the assumption is valid in the load's context.
+ if (OBU.getTagName() == "align" && OBU.Inputs.size() == 2) {
+ auto *LI = dyn_cast<LoadInst>(OBU.Inputs[0]);
+ if (!LI || !isValidAssumeForContext(II, LI, &DT, /*AllowEphemerals=*/true))
+ continue;
+ auto *Align = cast<ConstantInt>(OBU.Inputs[1]);
+ if (!isPowerOf2_64(Align->getZExtValue()))
+ continue;
+ LI->setMetadata(LLVMContext::MD_align,
+ MDNode::get(II->getContext(),
+ ValueAsMetadata::getConstant(
+ Align)));
+ auto *New = CallBase::removeOperandBundle(II, OBU.getTagID());
+ return New;
+ }
}
// Convert nonnull assume like:
diff --git a/llvm/test/Transforms/InstCombine/assume-align.ll b/llvm/test/Transforms/InstCombine/assume-align.ll
index 2b8ca5d25fd1a8..65256377696a59 100644
--- a/llvm/test/Transforms/InstCombine/assume-align.ll
+++ b/llvm/test/Transforms/InstCombine/assume-align.ll
@@ -123,11 +123,9 @@ define i8 @assume_align_non_pow2(ptr %p) {
ret i8 %v
}
-; TODO: Can fold alignment assumption into !align metadata on load.
define ptr @fold_assume_align_pow2_of_loaded_pointer_into_align_metadata(ptr %p) {
; CHECK-LABEL: @fold_assume_align_pow2_of_loaded_pointer_into_align_metadata(
-; CHECK-NEXT: [[P2:%.*]] = load ptr, ptr [[P:%.*]], align 8
-; CHECK-NEXT: call void @llvm.assume(i1 true) [ "align"(ptr [[P2]], i64 8) ]
+; CHECK-NEXT: [[P2:%.*]] = load ptr, ptr [[P:%.*]], align 8, !align [[META0:![0-9]+]]
; CHECK-NEXT: ret ptr [[P2]]
;
%p2 = load ptr, ptr %p
@@ -171,3 +169,6 @@ define ptr @dont_fold_assume_align_zero_of_loaded_pointer_into_align_metadata(pt
call void @llvm.assume(i1 true) [ "align"(ptr %p2, i64 0) ]
ret ptr %p2
}
+;.
+; CHECK: [[META0]] = !{i64 8}
+;.
>From 27c0fb065d1da544ea470bcef43801d51073510a Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Tue, 17 Sep 2024 12:09:07 +0100
Subject: [PATCH 2/3] !fix formatting.
---
.../InstCombine/InstCombineCalls.cpp | 21 ++++++++++---------
1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 596de10e20b6de..bff44e11c3ab8d 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3079,10 +3079,10 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
for (unsigned Idx = 0; Idx < II->getNumOperandBundles(); Idx++) {
OperandBundleUse OBU = II->getOperandBundleAt(Idx);
- // Separate storage assumptions apply to the underlying allocations, not any
- // particular pointer within them. When evaluating the hints for AA purposes
- // we getUnderlyingObject them; by precomputing the answers here we can
- // avoid having to do so repeatedly there.
+ // Separate storage assumptions apply to the underlying allocations, not
+ // any particular pointer within them. When evaluating the hints for AA
+ // purposes we getUnderlyingObject them; by precomputing the answers here
+ // we can avoid having to do so repeatedly there.
if (OBU.getTagName() == "separate_storage") {
assert(OBU.Inputs.size() == 2);
auto MaybeSimplifyHint = [&](const Use &U) {
@@ -3097,18 +3097,19 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
MaybeSimplifyHint(OBU.Inputs[1]);
}
- // Try to fold alignment assumption into a load's !align metadata, if the assumption is valid in the load's context.
+ // Try to fold alignment assumption into a load's !align metadata, if the
+ // assumption is valid in the load's context.
if (OBU.getTagName() == "align" && OBU.Inputs.size() == 2) {
auto *LI = dyn_cast<LoadInst>(OBU.Inputs[0]);
- if (!LI || !isValidAssumeForContext(II, LI, &DT, /*AllowEphemerals=*/true))
+ if (!LI ||
+ !isValidAssumeForContext(II, LI, &DT, /*AllowEphemerals=*/true))
continue;
auto *Align = cast<ConstantInt>(OBU.Inputs[1]);
if (!isPowerOf2_64(Align->getZExtValue()))
continue;
- LI->setMetadata(LLVMContext::MD_align,
- MDNode::get(II->getContext(),
- ValueAsMetadata::getConstant(
- Align)));
+ LI->setMetadata(
+ LLVMContext::MD_align,
+ MDNode::get(II->getContext(), ValueAsMetadata::getConstant(Align)));
auto *New = CallBase::removeOperandBundle(II, OBU.getTagID());
return New;
}
>From 6f10d942885e2a86436ce9d4e39627d463c8386b Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Tue, 17 Sep 2024 13:04:56 +0100
Subject: [PATCH 3/3] !fixup check alignment is ConstantInt.
---
.../lib/Transforms/InstCombine/InstCombineCalls.cpp | 4 ++--
llvm/test/Transforms/InstCombine/assume-align.ll | 13 +++++++++++++
2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index bff44e11c3ab8d..66ceda9aa42643 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3104,8 +3104,8 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
if (!LI ||
!isValidAssumeForContext(II, LI, &DT, /*AllowEphemerals=*/true))
continue;
- auto *Align = cast<ConstantInt>(OBU.Inputs[1]);
- if (!isPowerOf2_64(Align->getZExtValue()))
+ auto *Align = dyn_cast<ConstantInt>(OBU.Inputs[1]);
+ if (!Align || !isPowerOf2_64(Align->getZExtValue()))
continue;
LI->setMetadata(
LLVMContext::MD_align,
diff --git a/llvm/test/Transforms/InstCombine/assume-align.ll b/llvm/test/Transforms/InstCombine/assume-align.ll
index 65256377696a59..9d9f18068bb3e8 100644
--- a/llvm/test/Transforms/InstCombine/assume-align.ll
+++ b/llvm/test/Transforms/InstCombine/assume-align.ll
@@ -169,6 +169,19 @@ define ptr @dont_fold_assume_align_zero_of_loaded_pointer_into_align_metadata(pt
call void @llvm.assume(i1 true) [ "align"(ptr %p2, i64 0) ]
ret ptr %p2
}
+
+; !align must have a constant integer alignment.
+define ptr @dont_fold_assume_align_not_constant_of_loaded_pointer_into_align_metadata(ptr %p, i64 %align) {
+; CHECK-LABEL: @dont_fold_assume_align_not_constant_of_loaded_pointer_into_align_metadata(
+; CHECK-NEXT: [[P2:%.*]] = load ptr, ptr [[P:%.*]], align 8
+; CHECK-NEXT: call void @llvm.assume(i1 true) [ "align"(ptr [[P2]], i64 [[ALIGN:%.*]]) ]
+; CHECK-NEXT: ret ptr [[P2]]
+;
+ %p2 = load ptr, ptr %p
+ call void @llvm.assume(i1 true) [ "align"(ptr %p2, i64 %align) ]
+ ret ptr %p2
+}
+
;.
; CHECK: [[META0]] = !{i64 8}
;.
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