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Prevent Constant Folding From Optimizing inrange GEP

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This patch does the following things:

1. update SymbolicallyEvaluateGEP so that it bails out if it cannot preserve inrange arribute;
2. update llvm/test/Analysis/ConstantFolding/gep.ll to remove UB in it;
3. remove inaccurate comment above ConstantFoldInstOperandsImpl in llvm/lib/Analysis/ConstantFolding.cpp;
4. add a new regression test that makes sure that no optimizations change an inrange GEP in an unexpected way.

Patch by Zhaomo Yang!

Differential Revision: https://reviews.llvm.org/D51698

llvm-svn: 341888
This commit is contained in:
Peter Collingbourne 2018-09-11 01:53:36 +00:00
parent 54bc26f33d
commit b6e7ff238c
3 changed files with 32 additions and 24 deletions
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11
lib/Analysis/ConstantFolding.cpp
View File

@ -960,10 +960,8 @@ Constant *SymbolicallyEvaluateGEP(const GEPOperator *GEP,
NewIdxs.size() > *LastIRIndex) {
InRangeIndex = LastIRIndex;
for (unsigned I = 0; I <= *LastIRIndex; ++I)
if (NewIdxs[I] != InnermostGEP->getOperand(I + 1)) {
InRangeIndex = None;
break;
}
if (NewIdxs[I] != InnermostGEP->getOperand(I + 1))
return nullptr;
}
// Create a GEP.
@ -985,11 +983,6 @@ Constant *SymbolicallyEvaluateGEP(const GEPOperator *GEP,
/// returned, if not, null is returned. Note that this function can fail when
/// attempting to fold instructions like loads and stores, which have no
/// constant expression form.
///
/// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/inrange
/// etc information, due to only being passed an opcode and operands. Constant
/// folding using this function strips this information.
///
Constant *ConstantFoldInstOperandsImpl(const Value *InstOrCE, unsigned Opcode,
ArrayRef<Constant *> Ops,
const DataLayout &DL,

27
test/Analysis/ConstantFolding/gep.ll
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@ -8,23 +8,20 @@ target triple = "x86_64-unknown-linux-gnu"
@vt = external global [3 x i8*]
; CHECK: define i32 (...)* @f0()
define i32 (...)* @f0() {
; CHECK-NEXT: load i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, inrange i64 0, i64 2) to i32 (...)**)
%load = load i32 (...)*, i32 (...)** getelementptr (i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, inrange i64 0, i64 1) to i32 (...)**), i64 1)
ret i32 (...)* %load
; CHECK: define i32 (...)** @f0()
define i32 (...)** @f0() {
; CHECK-NEXT: ret i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, inrange i64 0, i64 2) to i32 (...)**
ret i32 (...)** getelementptr (i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, inrange i64 0, i64 1) to i32 (...)**), i64 1)
}
; CHECK: define i32 (...)* @f1()
define i32 (...)* @f1() {
; CHECK-NEXT: load i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, i64 0, i64 2) to i32 (...)**)
%load = load i32 (...)*, i32 (...)** getelementptr (i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, i64 0, inrange i64 1) to i32 (...)**), i64 1)
ret i32 (...)* %load
; CHECK: define i32 (...)** @f1()
define i32 (...)** @f1() {
; CHECK-NEXT: ret i32 (...)** getelementptr (i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, i64 0, inrange i64 1) to i32 (...)**), i64 1)
ret i32 (...)** getelementptr (i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, i64 0, inrange i64 1) to i32 (...)**), i64 1)
}
; CHECK: define i32 (...)* @f2()
define i32 (...)* @f2() {
; CHECK-NEXT: load i32 (...)*, i32 (...)** bitcast (i8** getelementptr ([3 x i8*], [3 x i8*]* @vt, i64 1, i64 1) to i32 (...)**)
%load = load i32 (...)*, i32 (...)** getelementptr (i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, i64 0, inrange i64 1) to i32 (...)**), i64 3)
ret i32 (...)* %load
; CHECK: define i32 (...)** @f2()
define i32 (...)** @f2() {
; CHECK-NEXT: ret i32 (...)** getelementptr (i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, i64 0, inrange i64 1) to i32 (...)**), i64 3)
ret i32 (...)** getelementptr (i32 (...)*, i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @vt, i64 0, inrange i64 1) to i32 (...)**), i64 3)
}

18
test/Other/optimize-inrange-gep.ll Normal file
View File

@ -0,0 +1,18 @@
; RUN: opt -O0 -S < %s | FileCheck %s
; RUN: opt -O1 -S < %s | FileCheck %s
; RUN: opt -O2 -S < %s | FileCheck %s
; RUN: opt -O3 -S < %s | FileCheck %s
; RUN: opt -Os -S < %s | FileCheck %s
; RUN: opt -Oz -S < %s | FileCheck %s
target datalayout = "e-p:64:64"
; Make sure that optimizations do not optimize inrange GEP.
@vtable = constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* null] }
define void @foo(i8*** %p) {
;CHECK: store i8** getelementptr {{.*}} ({ [3 x i8*] }, { [3 x i8*] }* @vtable, i{{.*}} 0, inrange i32 0, i{{.*}} 3), i8*** %p
store i8** getelementptr ({ [3 x i8*] }, { [3 x i8*] }* @vtable, i32 0, inrange i32 0, i32 3), i8*** %p
ret void
}