[llvm] [InstCombine] Relax the same-underlying-object constraint for the GEP canonicalization (PR #76583)
Yingwei Zheng via llvm-commits
llvm-commits at lists.llvm.org
Sun Dec 31 07:37:16 PST 2023
https://github.com/dtcxzyw updated https://github.com/llvm/llvm-project/pull/76583
>From 17833261101533fcb6a4ba71fa02f9e5b36cb4fb Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sat, 30 Dec 2023 15:33:01 +0800
Subject: [PATCH 1/5] [InstCombine] Add pre-commit tests. NFC.
---
.../Transforms/InstCombine/getelementptr.ll | 90 +++++++++++++++++++
1 file changed, 90 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/getelementptr.ll b/llvm/test/Transforms/InstCombine/getelementptr.ll
index 7d67f2583aa24d..18373a9222f8d8 100644
--- a/llvm/test/Transforms/InstCombine/getelementptr.ll
+++ b/llvm/test/Transforms/InstCombine/getelementptr.ll
@@ -1537,4 +1537,94 @@ define ptr @gep_ashr_without_exact(ptr %p, i64 %off) {
ret ptr %ptr
}
+define i1 @test_only_used_by_icmp(ptr %a, ptr %b, ptr %c) {
+; CHECK-LABEL: @test_only_used_by_icmp(
+; CHECK-NEXT: [[PA:%.*]] = ptrtoint ptr [[A:%.*]] to i64
+; CHECK-NEXT: [[PB:%.*]] = ptrtoint ptr [[B:%.*]] to i64
+; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PB]], [[PA]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 [[SUB]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[GEP]], [[C:%.*]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %pa = ptrtoint ptr %a to i64
+ %pb = ptrtoint ptr %b to i64
+ %sub = sub i64 %pb, %pa
+ %gep = getelementptr i8, ptr %a, i64 %sub
+ %cmp = icmp eq ptr %gep, %c
+ ret i1 %cmp
+}
+
+define i64 @test_only_used_by_ptrtoint(ptr %a, ptr %b) {
+; CHECK-LABEL: @test_only_used_by_ptrtoint(
+; CHECK-NEXT: [[PA:%.*]] = ptrtoint ptr [[A:%.*]] to i64
+; CHECK-NEXT: [[PB:%.*]] = ptrtoint ptr [[B:%.*]] to i64
+; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PB]], [[PA]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 [[SUB]]
+; CHECK-NEXT: [[VAL:%.*]] = ptrtoint ptr [[GEP]] to i64
+; CHECK-NEXT: ret i64 [[VAL]]
+;
+ %pa = ptrtoint ptr %a to i64
+ %pb = ptrtoint ptr %b to i64
+ %sub = sub i64 %pb, %pa
+ %gep = getelementptr i8, ptr %a, i64 %sub
+ %val = ptrtoint ptr %gep to i64
+ ret i64 %val
+}
+
+define i64 @test_used_by_both(ptr %a, ptr %b, ptr %c) {
+; CHECK-LABEL: @test_used_by_both(
+; CHECK-NEXT: [[PA:%.*]] = ptrtoint ptr [[A:%.*]] to i64
+; CHECK-NEXT: [[PB:%.*]] = ptrtoint ptr [[B:%.*]] to i64
+; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PB]], [[PA]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 [[SUB]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[GEP]], [[C:%.*]]
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[VAL:%.*]] = ptrtoint ptr [[GEP]] to i64
+; CHECK-NEXT: ret i64 [[VAL]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i64 0
+;
+ %pa = ptrtoint ptr %a to i64
+ %pb = ptrtoint ptr %b to i64
+ %sub = sub i64 %pb, %pa
+ %gep = getelementptr i8, ptr %a, i64 %sub
+ %cmp = icmp eq ptr %gep, %c
+ br i1 %cmp, label %if.then, label %if.else
+if.then:
+ %val = ptrtoint ptr %gep to i64
+ ret i64 %val
+if.else:
+ ret i64 0
+}
+
+; Negative tests
+
+define i64 @test_used_by_both_invalid(ptr %a, ptr %b, ptr %c) {
+; CHECK-LABEL: @test_used_by_both_invalid(
+; CHECK-NEXT: [[PA:%.*]] = ptrtoint ptr [[A:%.*]] to i64
+; CHECK-NEXT: [[PB:%.*]] = ptrtoint ptr [[B:%.*]] to i64
+; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PB]], [[PA]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 [[SUB]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[GEP]], [[C:%.*]]
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[VAL:%.*]] = load i64, ptr [[GEP]], align 8
+; CHECK-NEXT: ret i64 [[VAL]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i64 0
+;
+ %pa = ptrtoint ptr %a to i64
+ %pb = ptrtoint ptr %b to i64
+ %sub = sub i64 %pb, %pa
+ %gep = getelementptr i8, ptr %a, i64 %sub
+ %cmp = icmp eq ptr %gep, %c
+ br i1 %cmp, label %if.then, label %if.else
+if.then:
+ %val = load i64, ptr %gep, align 8
+ ret i64 %val
+if.else:
+ ret i64 0
+}
+
!0 = !{!"branch_weights", i32 2, i32 10}
>From eaf4836f014fb295baca4563260da7bf27ff7f51 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sat, 30 Dec 2023 15:34:39 +0800
Subject: [PATCH 2/5] [InstCombine] Relax the same-underlying-object constraint
for the GEP canonicalization
---
.../InstCombine/InstructionCombining.cpp | 11 +++++++---
.../Transforms/InstCombine/getelementptr.ll | 20 ++++---------------
2 files changed, 12 insertions(+), 19 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index df393d72a85bf2..5b2b7d84e4717b 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2471,13 +2471,18 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
if (TyAllocSize == 1) {
// Canonicalize (gep i8* X, (ptrtoint Y)-(ptrtoint X)) to (bitcast Y),
- // but only if both point to the same underlying object (otherwise
- // provenance is not necessarily retained).
+ // but only if the result pointer is only used as if it were an integer,
+ // or both point to the same underlying object (otherwise provenance is
+ // not necessarily retained).
Value *X = GEP.getPointerOperand();
Value *Y;
if (match(GEP.getOperand(1),
m_Sub(m_PtrToInt(m_Value(Y)), m_PtrToInt(m_Specific(X)))) &&
- getUnderlyingObject(X) == getUnderlyingObject(Y))
+ (all_of(GEP.users(),
+ [](User *U) {
+ return isa<ICmpInst>(U) || isa<PtrToIntInst>(U);
+ }) ||
+ getUnderlyingObject(X) == getUnderlyingObject(Y)))
return CastInst::CreatePointerBitCastOrAddrSpaceCast(Y, GEPType);
} else {
// Canonicalize (gep T* X, V / sizeof(T)) to (gep i8* X, V)
diff --git a/llvm/test/Transforms/InstCombine/getelementptr.ll b/llvm/test/Transforms/InstCombine/getelementptr.ll
index 18373a9222f8d8..22c918e0d4a3ea 100644
--- a/llvm/test/Transforms/InstCombine/getelementptr.ll
+++ b/llvm/test/Transforms/InstCombine/getelementptr.ll
@@ -1539,11 +1539,7 @@ define ptr @gep_ashr_without_exact(ptr %p, i64 %off) {
define i1 @test_only_used_by_icmp(ptr %a, ptr %b, ptr %c) {
; CHECK-LABEL: @test_only_used_by_icmp(
-; CHECK-NEXT: [[PA:%.*]] = ptrtoint ptr [[A:%.*]] to i64
-; CHECK-NEXT: [[PB:%.*]] = ptrtoint ptr [[B:%.*]] to i64
-; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PB]], [[PA]]
-; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 [[SUB]]
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[GEP]], [[C:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[B:%.*]], [[C:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%pa = ptrtoint ptr %a to i64
@@ -1556,11 +1552,7 @@ define i1 @test_only_used_by_icmp(ptr %a, ptr %b, ptr %c) {
define i64 @test_only_used_by_ptrtoint(ptr %a, ptr %b) {
; CHECK-LABEL: @test_only_used_by_ptrtoint(
-; CHECK-NEXT: [[PA:%.*]] = ptrtoint ptr [[A:%.*]] to i64
-; CHECK-NEXT: [[PB:%.*]] = ptrtoint ptr [[B:%.*]] to i64
-; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PB]], [[PA]]
-; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 [[SUB]]
-; CHECK-NEXT: [[VAL:%.*]] = ptrtoint ptr [[GEP]] to i64
+; CHECK-NEXT: [[VAL:%.*]] = ptrtoint ptr [[B:%.*]] to i64
; CHECK-NEXT: ret i64 [[VAL]]
;
%pa = ptrtoint ptr %a to i64
@@ -1573,14 +1565,10 @@ define i64 @test_only_used_by_ptrtoint(ptr %a, ptr %b) {
define i64 @test_used_by_both(ptr %a, ptr %b, ptr %c) {
; CHECK-LABEL: @test_used_by_both(
-; CHECK-NEXT: [[PA:%.*]] = ptrtoint ptr [[A:%.*]] to i64
-; CHECK-NEXT: [[PB:%.*]] = ptrtoint ptr [[B:%.*]] to i64
-; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PB]], [[PA]]
-; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 [[SUB]]
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[GEP]], [[C:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[B:%.*]], [[C:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
-; CHECK-NEXT: [[VAL:%.*]] = ptrtoint ptr [[GEP]] to i64
+; CHECK-NEXT: [[VAL:%.*]] = ptrtoint ptr [[B]] to i64
; CHECK-NEXT: ret i64 [[VAL]]
; CHECK: if.else:
; CHECK-NEXT: ret i64 0
>From 590215ff99666a00514a9eb40ebe79fa486b161f Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sun, 31 Dec 2023 18:07:23 +0800
Subject: [PATCH 3/5] fixup! [InstCombine] Relax the same-underlying-object
constraint for the GEP canonicalization
---
.../InstCombine/InstructionCombining.cpp | 32 +++++++++++++++----
.../Transforms/InstCombine/getelementptr.ll | 8 ++---
2 files changed, 29 insertions(+), 11 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 5b2b7d84e4717b..33585afec5f802 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2477,13 +2477,31 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Value *X = GEP.getPointerOperand();
Value *Y;
if (match(GEP.getOperand(1),
- m_Sub(m_PtrToInt(m_Value(Y)), m_PtrToInt(m_Specific(X)))) &&
- (all_of(GEP.users(),
- [](User *U) {
- return isa<ICmpInst>(U) || isa<PtrToIntInst>(U);
- }) ||
- getUnderlyingObject(X) == getUnderlyingObject(Y)))
- return CastInst::CreatePointerBitCastOrAddrSpaceCast(Y, GEPType);
+ m_Sub(m_PtrToInt(m_Value(Y)), m_PtrToInt(m_Specific(X))))) {
+ std::optional<bool> HasSameUnderlyingObjectCache;
+ auto HasSameUnderlyingObject = [&] {
+ if (!HasSameUnderlyingObjectCache)
+ HasSameUnderlyingObjectCache =
+ getUnderlyingObject(X) == getUnderlyingObject(Y);
+ return *HasSameUnderlyingObjectCache;
+ };
+ std::optional<Value *> CastedValueCache;
+ auto GetCastedValue = [&] {
+ if (!CastedValueCache)
+ CastedValueCache =
+ Builder.CreatePointerBitCastOrAddrSpaceCast(Y, GEPType);
+ return *CastedValueCache;
+ };
+
+ bool Changed = false;
+ for (User *U : GEP.users())
+ if (isa<ICmpInst>(U) || isa<PtrToIntInst>(U) ||
+ HasSameUnderlyingObject()) {
+ U->replaceUsesOfWith(&GEP, GetCastedValue());
+ Changed = true;
+ }
+ return Changed ? &GEP : nullptr;
+ }
} else {
// Canonicalize (gep T* X, V / sizeof(T)) to (gep i8* X, V)
Value *V;
diff --git a/llvm/test/Transforms/InstCombine/getelementptr.ll b/llvm/test/Transforms/InstCombine/getelementptr.ll
index 22c918e0d4a3ea..373b7f5f2fc0a5 100644
--- a/llvm/test/Transforms/InstCombine/getelementptr.ll
+++ b/llvm/test/Transforms/InstCombine/getelementptr.ll
@@ -1590,13 +1590,13 @@ if.else:
define i64 @test_used_by_both_invalid(ptr %a, ptr %b, ptr %c) {
; CHECK-LABEL: @test_used_by_both_invalid(
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[B:%.*]], [[C:%.*]]
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[PB:%.*]] = ptrtoint ptr [[B]] to i64
; CHECK-NEXT: [[PA:%.*]] = ptrtoint ptr [[A:%.*]] to i64
-; CHECK-NEXT: [[PB:%.*]] = ptrtoint ptr [[B:%.*]] to i64
; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[PB]], [[PA]]
; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[A]], i64 [[SUB]]
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[GEP]], [[C:%.*]]
-; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
-; CHECK: if.then:
; CHECK-NEXT: [[VAL:%.*]] = load i64, ptr [[GEP]], align 8
; CHECK-NEXT: ret i64 [[VAL]]
; CHECK: if.else:
>From 32263bdf1e57261e1c8789d787f63fe35d533b05 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sun, 31 Dec 2023 20:38:42 +0800
Subject: [PATCH 4/5] fixup! [InstCombine] Relax the same-underlying-object
constraint for the GEP canonicalization
---
.../InstCombine/InstructionCombining.cpp | 33 +++++++------------
1 file changed, 11 insertions(+), 22 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 33585afec5f802..c453a0f1fa50f5 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2477,29 +2477,18 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Value *X = GEP.getPointerOperand();
Value *Y;
if (match(GEP.getOperand(1),
- m_Sub(m_PtrToInt(m_Value(Y)), m_PtrToInt(m_Specific(X))))) {
- std::optional<bool> HasSameUnderlyingObjectCache;
- auto HasSameUnderlyingObject = [&] {
- if (!HasSameUnderlyingObjectCache)
- HasSameUnderlyingObjectCache =
- getUnderlyingObject(X) == getUnderlyingObject(Y);
- return *HasSameUnderlyingObjectCache;
- };
- std::optional<Value *> CastedValueCache;
- auto GetCastedValue = [&] {
- if (!CastedValueCache)
- CastedValueCache =
- Builder.CreatePointerBitCastOrAddrSpaceCast(Y, GEPType);
- return *CastedValueCache;
- };
-
+ m_Sub(m_PtrToInt(m_Value(Y)), m_PtrToInt(m_Specific(X)))) &&
+ GEPType == Y->getType()) {
+ bool hasSameUnderlyingObject =
+ getUnderlyingObject(X) == getUnderlyingObject(Y);
bool Changed = false;
- for (User *U : GEP.users())
- if (isa<ICmpInst>(U) || isa<PtrToIntInst>(U) ||
- HasSameUnderlyingObject()) {
- U->replaceUsesOfWith(&GEP, GetCastedValue());
- Changed = true;
- }
+ GEP.replaceUsesWithIf(Y, [&](Use &U) {
+ bool ShouldReplace = hasSameUnderlyingObject ||
+ isa<ICmpInst>(U.getUser()) ||
+ isa<PtrToIntInst>(U.getUser());
+ Changed |= ShouldReplace;
+ return ShouldReplace;
+ });
return Changed ? &GEP : nullptr;
}
} else {
>From 67c89f168f5b8370eb5d7e461b6c2bf6664e85d9 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw at qq.com>
Date: Sun, 31 Dec 2023 23:37:09 +0800
Subject: [PATCH 5/5] Update
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
Co-authored-by: Nikita Popov <github at npopov.com>
---
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index c453a0f1fa50f5..f2909ce1425a86 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2479,7 +2479,7 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
if (match(GEP.getOperand(1),
m_Sub(m_PtrToInt(m_Value(Y)), m_PtrToInt(m_Specific(X)))) &&
GEPType == Y->getType()) {
- bool hasSameUnderlyingObject =
+ bool HasSameUnderlyingObject =
getUnderlyingObject(X) == getUnderlyingObject(Y);
bool Changed = false;
GEP.replaceUsesWithIf(Y, [&](Use &U) {
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