[llvm] [InstCombine] Convert mem intrinsic with null into a noop (PR #100388)
Yingwei Zheng via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 24 07:52:10 PDT 2024
https://github.com/dtcxzyw updated https://github.com/llvm/llvm-project/pull/100388
>From a61d61371b818b9fa0976a7d1fa0d32aab7c7208 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Wed, 24 Jul 2024 22:08:30 +0800
Subject: [PATCH 1/3] [InstCombine] Add pre-commit tests. NFC.
---
.../Transforms/InstCombine/mem-intrinsics.ll | 73 +++++++++++++++++++
1 file changed, 73 insertions(+)
create mode 100644 llvm/test/Transforms/InstCombine/mem-intrinsics.ll
diff --git a/llvm/test/Transforms/InstCombine/mem-intrinsics.ll b/llvm/test/Transforms/InstCombine/mem-intrinsics.ll
new file mode 100644
index 0000000000000..73619f81115f0
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/mem-intrinsics.ll
@@ -0,0 +1,73 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instcombine < %s | FileCheck %s
+
+define void @memset_null(i64 %len) {
+; CHECK-LABEL: define void @memset_null(
+; CHECK-SAME: i64 [[LEN:%.*]]) {
+; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 4294967296 null, i8 0, i64 [[LEN]], i1 false)
+; CHECK-NEXT: ret void
+;
+ call void @llvm.memset.p0.i64(ptr null, i8 0, i64 %len, i1 false)
+ ret void
+}
+
+define void @memset_null_ub() {
+; CHECK-LABEL: define void @memset_null_ub() {
+; CHECK-NEXT: store i64 poison, ptr null, align 4294967296
+; CHECK-NEXT: ret void
+;
+ call void @llvm.memset.p0.i64(ptr null, i8 0, i64 8, i1 false)
+ ret void
+}
+
+define void @memcpy_null_src(ptr %dst, i64 %len) {
+; CHECK-LABEL: define void @memcpy_null_src(
+; CHECK-SAME: ptr [[DST:%.*]], i64 [[LEN:%.*]]) {
+; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[DST]], ptr align 4294967296 null, i64 [[LEN]], i1 false)
+; CHECK-NEXT: ret void
+;
+ call void @llvm.memcpy.p0.i64(ptr %dst, ptr null, i64 %len, i1 false)
+ ret void
+}
+
+define void @memmove_null_src(ptr %dst, i64 %len) {
+; CHECK-LABEL: define void @memmove_null_src(
+; CHECK-SAME: ptr [[DST:%.*]], i64 [[LEN:%.*]]) {
+; CHECK-NEXT: call void @llvm.memmove.p0.p0.i64(ptr align 1 [[DST]], ptr align 4294967296 null, i64 [[LEN]], i1 false)
+; CHECK-NEXT: ret void
+;
+ call void @llvm.memmove.p0.i64(ptr %dst, ptr null, i64 %len, i1 false)
+ ret void
+}
+
+define void @memset_element_atomic(i64 %len) {
+; CHECK-LABEL: define void @memset_element_atomic(
+; CHECK-SAME: i64 [[LEN:%.*]]) {
+; CHECK-NEXT: call void @llvm.memset.element.unordered.atomic.p0.i64(ptr align 4294967296 null, i8 0, i64 [[LEN]], i32 1)
+; CHECK-NEXT: ret void
+;
+ call void @llvm.memset.element.unordered.atomic.p0.i64(ptr align 1 null, i8 0, i64 %len, i32 1)
+ ret void
+}
+
+; negative tests
+
+define void @memset_null_volatile(i64 %len) {
+; CHECK-LABEL: define void @memset_null_volatile(
+; CHECK-SAME: i64 [[LEN:%.*]]) {
+; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr null, i8 0, i64 [[LEN]], i1 true)
+; CHECK-NEXT: ret void
+;
+ call void @llvm.memset.p0.i64(ptr null, i8 0, i64 %len, i1 true)
+ ret void
+}
+
+define void @memset_null_is_defined(i64 %len) null_pointer_is_valid {
+; CHECK-LABEL: define void @memset_null_is_defined(
+; CHECK-SAME: i64 [[LEN:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 4294967296 null, i8 0, i64 [[LEN]], i1 false)
+; CHECK-NEXT: ret void
+;
+ call void @llvm.memset.p0.i64(ptr null, i8 0, i64 %len, i1 false)
+ ret void
+}
>From 598cf9261511f0fcabe659697f9c9aec0d522544 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Wed, 24 Jul 2024 22:19:03 +0800
Subject: [PATCH 2/3] [InstCombine] Convert mem intrinsic with null into a noop
---
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp | 9 +++++++++
llvm/test/Transforms/InstCombine/mem-intrinsics.ll | 12 ++++++++----
llvm/test/Transforms/InstCombine/mempcpy.ll | 2 +-
3 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 3502bbbbeae25..aab915fd97902 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1575,16 +1575,25 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
return eraseInstFromFunction(CI);
}
+ bool SrcIsNull = false;
// If we can determine a pointer alignment that is bigger than currently
// set, update the alignment.
if (auto *MTI = dyn_cast<AnyMemTransferInst>(MI)) {
if (Instruction *I = SimplifyAnyMemTransfer(MTI))
return I;
+ SrcIsNull = isa<ConstantPointerNull>(MTI->getRawSource());
} else if (auto *MSI = dyn_cast<AnyMemSetInst>(MI)) {
if (Instruction *I = SimplifyAnyMemSet(MSI))
return I;
}
+ // If src/dest is null, this memory intrinsic must be a noop.
+ if (!NullPointerIsDefined(MI->getFunction()) &&
+ (SrcIsNull || isa<ConstantPointerNull>(MI->getRawDest()))) {
+ Builder.CreateAssumption(Builder.CreateIsNull(MI->getLength()));
+ return eraseInstFromFunction(CI);
+ }
+
if (Changed) return II;
}
diff --git a/llvm/test/Transforms/InstCombine/mem-intrinsics.ll b/llvm/test/Transforms/InstCombine/mem-intrinsics.ll
index 73619f81115f0..5448d3c20fb12 100644
--- a/llvm/test/Transforms/InstCombine/mem-intrinsics.ll
+++ b/llvm/test/Transforms/InstCombine/mem-intrinsics.ll
@@ -4,7 +4,8 @@
define void @memset_null(i64 %len) {
; CHECK-LABEL: define void @memset_null(
; CHECK-SAME: i64 [[LEN:%.*]]) {
-; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 4294967296 null, i8 0, i64 [[LEN]], i1 false)
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i64 [[LEN]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[TMP1]])
; CHECK-NEXT: ret void
;
call void @llvm.memset.p0.i64(ptr null, i8 0, i64 %len, i1 false)
@@ -23,7 +24,8 @@ define void @memset_null_ub() {
define void @memcpy_null_src(ptr %dst, i64 %len) {
; CHECK-LABEL: define void @memcpy_null_src(
; CHECK-SAME: ptr [[DST:%.*]], i64 [[LEN:%.*]]) {
-; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[DST]], ptr align 4294967296 null, i64 [[LEN]], i1 false)
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i64 [[LEN]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[TMP1]])
; CHECK-NEXT: ret void
;
call void @llvm.memcpy.p0.i64(ptr %dst, ptr null, i64 %len, i1 false)
@@ -33,7 +35,8 @@ define void @memcpy_null_src(ptr %dst, i64 %len) {
define void @memmove_null_src(ptr %dst, i64 %len) {
; CHECK-LABEL: define void @memmove_null_src(
; CHECK-SAME: ptr [[DST:%.*]], i64 [[LEN:%.*]]) {
-; CHECK-NEXT: call void @llvm.memmove.p0.p0.i64(ptr align 1 [[DST]], ptr align 4294967296 null, i64 [[LEN]], i1 false)
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i64 [[LEN]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[TMP1]])
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0.i64(ptr %dst, ptr null, i64 %len, i1 false)
@@ -43,7 +46,8 @@ define void @memmove_null_src(ptr %dst, i64 %len) {
define void @memset_element_atomic(i64 %len) {
; CHECK-LABEL: define void @memset_element_atomic(
; CHECK-SAME: i64 [[LEN:%.*]]) {
-; CHECK-NEXT: call void @llvm.memset.element.unordered.atomic.p0.i64(ptr align 4294967296 null, i8 0, i64 [[LEN]], i32 1)
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i64 [[LEN]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[TMP1]])
; CHECK-NEXT: ret void
;
call void @llvm.memset.element.unordered.atomic.p0.i64(ptr align 1 null, i8 0, i64 %len, i32 1)
diff --git a/llvm/test/Transforms/InstCombine/mempcpy.ll b/llvm/test/Transforms/InstCombine/mempcpy.ll
index c996758a919d9..82c34f8a864ce 100644
--- a/llvm/test/Transforms/InstCombine/mempcpy.ll
+++ b/llvm/test/Transforms/InstCombine/mempcpy.ll
@@ -55,7 +55,7 @@ define ptr @memcpy_big_const_n(ptr %d, ptr nocapture readonly %s) {
define i32 @PR48810() {
; CHECK-LABEL: @PR48810(
-; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 1 undef, ptr align 4294967296 null, i64 undef, i1 false)
+; CHECK-NEXT: store i1 true, ptr poison, align 1
; CHECK-NEXT: ret i32 undef
;
%r = call dereferenceable(1) ptr @mempcpy(ptr undef, ptr null, i64 undef)
>From 5dd05ae6edff8dfceb2ea6963c2f0deccb05a831 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Wed, 24 Jul 2024 22:50:39 +0800
Subject: [PATCH 3/3] [InstCombine] Address review comment.
---
.../lib/Transforms/InstCombine/InstCombineCalls.cpp | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index aab915fd97902..69abe356c332d 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1575,21 +1575,26 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
return eraseInstFromFunction(CI);
}
- bool SrcIsNull = false;
+ auto IsPointerUndefined = [MI](Value *Ptr) {
+ return isa<ConstantPointerNull>(Ptr) &&
+ !NullPointerIsDefined(
+ MI->getFunction(),
+ cast<PointerType>(Ptr->getType())->getAddressSpace());
+ };
+ bool SrcIsUndefined = false;
// If we can determine a pointer alignment that is bigger than currently
// set, update the alignment.
if (auto *MTI = dyn_cast<AnyMemTransferInst>(MI)) {
if (Instruction *I = SimplifyAnyMemTransfer(MTI))
return I;
- SrcIsNull = isa<ConstantPointerNull>(MTI->getRawSource());
+ SrcIsUndefined = IsPointerUndefined(MTI->getRawSource());
} else if (auto *MSI = dyn_cast<AnyMemSetInst>(MI)) {
if (Instruction *I = SimplifyAnyMemSet(MSI))
return I;
}
// If src/dest is null, this memory intrinsic must be a noop.
- if (!NullPointerIsDefined(MI->getFunction()) &&
- (SrcIsNull || isa<ConstantPointerNull>(MI->getRawDest()))) {
+ if (SrcIsUndefined || IsPointerUndefined(MI->getRawDest())) {
Builder.CreateAssumption(Builder.CreateIsNull(MI->getLength()));
return eraseInstFromFunction(CI);
}
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