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[SimplifyLibCalls] avoid slicing 64-bit integers in an ILP32 build (PR #54739)

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Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D123472
This commit is contained in:
Martin Sebor 2022-04-26 16:26:09 -06:00
parent a0b8ab1ba3
commit ffed0cfcdb
3 changed files with 150 additions and 4 deletions
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13
llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
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@ -451,8 +451,11 @@ Value *LibCallSimplifier::optimizeStrNCmp(CallInst *CI, IRBuilderBase &B) {
// strncmp(x, y) -> cnst (if both x and y are constant strings)
if (HasStr1 && HasStr2) {
StringRef SubStr1 = Str1.substr(0, Length);
StringRef SubStr2 = Str2.substr(0, Length);
// Avoid truncating the 64-bit Length to 32 bits in ILP32.
StringRef::size_type MinLen1 = std::min((uint64_t)Str1.size(), Length);
StringRef::size_type MinLen2 = std::min((uint64_t)Str2.size(), Length);
StringRef SubStr1 = Str1.substr(0, MinLen1);
StringRef SubStr2 = Str2.substr(0, MinLen2);
return ConstantInt::get(CI->getType(), SubStr1.compare(SubStr2));
}
@ -1021,8 +1024,10 @@ Value *LibCallSimplifier::optimizeMemChr(CallInst *CI, IRBuilderBase &B) {
// From now on we need a constant length and constant array.
return nullptr;
// Truncate the string to LenC.
Str = Str.substr(0, LenC->getZExtValue());
// Truncate the string to LenC without slicing when targeting LP64
// on an ILP32 host.
uint64_t EndOff = std::min(LenC->getZExtValue(), (uint64_t)StringRef::npos);
Str = Str.substr(0, EndOff);
// If the char is variable but the input str and length are not we can turn
// this memchr call into a simple bit field test. Of course this only works

69
llvm/test/Transforms/InstCombine/memchr-4.ll Normal file
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@ -0,0 +1,69 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instcombine -S | FileCheck %s
; Verify that an excessive size to memchr() isn't truncated to an in-bounds
; value that results in the call being incorrectly folded (as might happen
; when LLVM is compiled in ILP32 mode).
declare i8* @memchr(i8*, i32, i64)
@ax = external global [0 x i8]
@a12345 = constant [5 x i8] c"\01\02\03\04\05"
; Do not fold memchr(ax, 1, UINT_MAX + (size_t)1) to null. Only the first
; byte in ax must be dereferenceable.
define i8* @call_memchr_ax_2_uimax_p1() {
; CHECK-LABEL: @call_memchr_ax_2_uimax_p1(
; CHECK-NEXT: [[RES:%.*]] = call i8* @memchr(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([0 x i8], [0 x i8]* @ax, i64 0, i64 0), i32 1, i64 4294967296)
; CHECK-NEXT: ret i8* [[RES]]
;
%ptr = getelementptr [0 x i8], [0 x i8]* @ax, i32 0, i32 0
%res = call i8* @memchr(i8* %ptr, i32 1, i64 4294967296)
ret i8* %res
}
; Do not fold memchr(ax, 1, UINT_MAX + (size_t)2) to *ax == 1 ? ax : null.
; As above, only the first byte in ax must be dereferenceable.
define i8* @call_memchr_ax_2_uimax_p2() {
; CHECK-LABEL: @call_memchr_ax_2_uimax_p2(
; CHECK-NEXT: [[RES:%.*]] = call i8* @memchr(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([0 x i8], [0 x i8]* @ax, i64 0, i64 0), i32 1, i64 4294967296)
; CHECK-NEXT: ret i8* [[RES]]
;
%ptr = getelementptr [0 x i8], [0 x i8]* @ax, i32 0, i32 0
%res = call i8* @memchr(i8* %ptr, i32 1, i64 4294967296)
ret i8* %res
}
; Fold memchr(a12345, 3, UINT_MAX + (size_t)2) to a12345 + 2 (and not to
; null).
define i8* @fold_memchr_a12345_3_uimax_p2() {
; CHECK-LABEL: @fold_memchr_a12345_3_uimax_p2(
; CHECK-NEXT: ret i8* getelementptr inbounds ([5 x i8], [5 x i8]* @a12345, i64 0, i64 2)
;
%ptr = getelementptr [5 x i8], [5 x i8]* @a12345, i32 0, i32 0
%res = call i8* @memchr(i8* %ptr, i32 3, i64 4294967297)
ret i8* %res
}
; Do not fold memchr(a12345, c, UINT_MAX + (size_t)2).
define i8* @fold_memchr_a12345_c_uimax_p2(i32 %0) {
; CHECK-LABEL: @fold_memchr_a12345_c_uimax_p2(
; CHECK-NEXT: [[RES:%.*]] = call i8* @memchr(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @a12345, i64 0, i64 0), i32 [[TMP0:%.*]], i64 4294967297)
; CHECK-NEXT: ret i8* [[RES]]
;
%ptr = getelementptr [5 x i8], [5 x i8]* @a12345, i32 0, i32 0
%res = call i8* @memchr(i8* %ptr, i32 %0, i64 4294967297)
ret i8* %res
}

72
llvm/test/Transforms/InstCombine/strncmp-3.ll Normal file
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@ -0,0 +1,72 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instcombine -S | FileCheck %s
; Verify that an excessive size to strncmp() isn't truncated to an in-bounds
; value that results in the call being incorrectly folded (as might happen
; when LLVM is compiled in ILP32 mode).
declare i32 @strncmp(i8*, i8*, i64)
@ax = external global [0 x i8]
@bx = external global [0 x i8]
@a12345 = constant [5 x i8] c"\01\02\03\04\05"
@a123456 = constant [6 x i8] c"\01\02\03\04\05\06"
; Do not fold strncmp(ax, bx, UINT_MAX + (size_t)1) to 0.
define i32 @call_strncmp_ax_bx_uimax_p1() {
; CHECK-LABEL: @call_strncmp_ax_bx_uimax_p1(
; CHECK-NEXT: [[RES:%.*]] = call i32 @strncmp(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([0 x i8], [0 x i8]* @ax, i64 0, i64 0), i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([0 x i8], [0 x i8]* @bx, i64 0, i64 0), i64 4294967296)
; CHECK-NEXT: ret i32 [[RES]]
;
%p1 = getelementptr [0 x i8], [0 x i8]* @ax, i32 0, i32 0
%p2 = getelementptr [0 x i8], [0 x i8]* @bx, i32 0, i32 0
%res = call i32 @strncmp(i8* %p1, i8* %p2, i64 4294967296)
ret i32 %res
}
; Do not fold strncmp(ax, bx, UINT_MAX + (size_t)2) to *ax - *bx.
define i32 @call_strncmp_ax_bx_uimax_p2() {
; CHECK-LABEL: @call_strncmp_ax_bx_uimax_p2(
; CHECK-NEXT: [[RES:%.*]] = call i32 @strncmp(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([0 x i8], [0 x i8]* @ax, i64 0, i64 0), i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([0 x i8], [0 x i8]* @bx, i64 0, i64 0), i64 4294967296)
; CHECK-NEXT: ret i32 [[RES]]
;
%p1 = getelementptr [0 x i8], [0 x i8]* @ax, i32 0, i32 0
%p2 = getelementptr [0 x i8], [0 x i8]* @bx, i32 0, i32 0
%res = call i32 @strncmp(i8* %p1, i8* %p2, i64 4294967296)
ret i32 %res
}
; Fold strncmp(a12345, a123456, UINT_MAX + (size_t)2) to -1 (and not to 0).
define i32 @fold_strncmp_a12345_2_uimax_p2() {
; CHECK-LABEL: @fold_strncmp_a12345_2_uimax_p2(
; CHECK-NEXT: ret i32 -1
;
%p1 = getelementptr [5 x i8], [5 x i8]* @a12345, i32 0, i32 0
%p2 = getelementptr [6 x i8], [6 x i8]* @a123456, i32 0, i32 0
%res = call i32 @strncmp(i8* %p1, i8* %p2, i64 4294967297)
ret i32 %res
}
; Fold strncmp(a123456, a12345, UINT_MAX + (size_t)3) to +1 (and not to 0).
define i32 @fold_strncmp_a12345_2_uimax_p3() {
; CHECK-LABEL: @fold_strncmp_a12345_2_uimax_p3(
; CHECK-NEXT: ret i32 1
;
%p1 = getelementptr [6 x i8], [6 x i8]* @a123456, i32 0, i32 0
%p2 = getelementptr [5 x i8], [5 x i8]* @a12345, i32 0, i32 0
%res = call i32 @strncmp(i8* %p1, i8* %p2, i64 4294967298)
ret i32 %res
}