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1291b464ba
This fixes a bug at LibCallSimplifier::optimizeMemChr which does the following transformation:
```
// memchr("\r\n", C, 2) != nullptr -> (1 << C & ((1 << '\r') | (1 << '\n')))
// != 0
// after bounds check.
```
As written above, a bounds check on C (whether it is less than integer bitwidth) is done before doing `1 << C` otherwise 1 << C will overflow.
If the bounds check is false, the result of (1 << C & ...) must not be used at all, otherwise the result of shift (which is poison) will contaminate the whole results.
A correct way to encode this is `select i1 (bounds check), (1 << C & ...), false` because select does not allow the unused operand to contaminate the result.
However, this optimization was introducing `and (bounds check), (1 << C & ...)` which cannot do that.
The bug was found from compilation of this C++ code: https://reviews.llvm.org/rG2fd3037ac615#1007197
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D104901
126 lines
4.1 KiB
LLVM
126 lines
4.1 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; Test that the strchr library call simplifier works correctly.
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; RUN: opt < %s -instcombine -S | FileCheck %s
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target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
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@hello = constant [14 x i8] c"hello world\5Cn\00"
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@null = constant [1 x i8] zeroinitializer
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@newlines = constant [3 x i8] c"\0D\0A\00"
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@chp = global i8* zeroinitializer
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declare i8* @strchr(i8*, i32)
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define void @test_simplify1() {
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; CHECK-LABEL: @test_simplify1(
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; CHECK-NEXT: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 6), i8** @chp, align 4
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; CHECK-NEXT: ret void
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;
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%str = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
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%dst = call i8* @strchr(i8* %str, i32 119)
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store i8* %dst, i8** @chp
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ret void
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}
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define void @test_simplify2() {
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; CHECK-LABEL: @test_simplify2(
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; CHECK-NEXT: store i8* null, i8** @chp, align 4
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; CHECK-NEXT: ret void
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;
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%str = getelementptr [1 x i8], [1 x i8]* @null, i32 0, i32 0
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%dst = call i8* @strchr(i8* %str, i32 119)
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store i8* %dst, i8** @chp
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ret void
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}
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define void @test_simplify3() {
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; CHECK-LABEL: @test_simplify3(
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; CHECK-NEXT: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 13), i8** @chp, align 4
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; CHECK-NEXT: ret void
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;
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%src = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
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%dst = call i8* @strchr(i8* %src, i32 0)
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store i8* %dst, i8** @chp
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ret void
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}
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define void @test_simplify4(i32 %chr) {
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; CHECK-LABEL: @test_simplify4(
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; CHECK-NEXT: [[MEMCHR:%.*]] = call i8* @memchr(i8* noundef nonnull dereferenceable(14) getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 0), i32 [[CHR:%.*]], i32 14)
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; CHECK-NEXT: store i8* [[MEMCHR]], i8** @chp, align 4
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; CHECK-NEXT: ret void
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;
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%src = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
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%dst = call i8* @strchr(i8* %src, i32 %chr)
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store i8* %dst, i8** @chp
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ret void
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}
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define void @test_simplify5() {
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; CHECK-LABEL: @test_simplify5(
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; CHECK-NEXT: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 13), i8** @chp, align 4
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; CHECK-NEXT: ret void
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;
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%src = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
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%dst = call i8* @strchr(i8* %src, i32 65280)
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store i8* %dst, i8** @chp
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ret void
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}
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; Check transformation strchr(p, 0) -> p + strlen(p)
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define void @test_simplify6(i8* %str) {
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; CHECK-LABEL: @test_simplify6(
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; CHECK-NEXT: [[STRLEN:%.*]] = call i32 @strlen(i8* noundef nonnull dereferenceable(1) [[STR:%.*]])
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; CHECK-NEXT: [[STRCHR:%.*]] = getelementptr i8, i8* [[STR]], i32 [[STRLEN]]
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; CHECK-NEXT: store i8* [[STRCHR]], i8** @chp, align 4
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; CHECK-NEXT: ret void
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;
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%dst = call i8* @strchr(i8* %str, i32 0)
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store i8* %dst, i8** @chp
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ret void
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}
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; Check transformation strchr("\r\n", C) != nullptr -> (C & 9217) != 0
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define i1 @test_simplify7(i32 %C) {
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; CHECK-LABEL: @test_simplify7(
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i32 [[C:%.*]] to i16
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; CHECK-NEXT: [[TMP2:%.*]] = and i16 [[TMP1]], 255
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; CHECK-NEXT: [[MEMCHR_BOUNDS:%.*]] = icmp ult i16 [[TMP2]], 16
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; CHECK-NEXT: [[TMP3:%.*]] = shl i16 1, [[TMP2]]
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; CHECK-NEXT: [[TMP4:%.*]] = and i16 [[TMP3]], 9217
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; CHECK-NEXT: [[MEMCHR_BITS:%.*]] = icmp ne i16 [[TMP4]], 0
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; CHECK-NEXT: [[MEMCHR1:%.*]] = select i1 [[MEMCHR_BOUNDS]], i1 [[MEMCHR_BITS]], i1 false
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; CHECK-NEXT: ret i1 [[MEMCHR1]]
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;
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%dst = call i8* @strchr(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @newlines, i64 0, i64 0), i32 %C)
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%cmp = icmp ne i8* %dst, null
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ret i1 %cmp
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}
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define i8* @test1(i8* %str, i32 %c) {
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; CHECK-LABEL: @test1(
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; CHECK-NEXT: [[RET:%.*]] = call i8* @strchr(i8* noundef nonnull dereferenceable(1) [[STR:%.*]], i32 [[C:%.*]])
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; CHECK-NEXT: ret i8* [[RET]]
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;
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%ret = call i8* @strchr(i8* %str, i32 %c)
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ret i8* %ret
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}
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define i8* @test2(i8* %str, i32 %c) null_pointer_is_valid {
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; CHECK-LABEL: @test2(
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; CHECK-NEXT: [[RET:%.*]] = call i8* @strchr(i8* noundef [[STR:%.*]], i32 [[C:%.*]])
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; CHECK-NEXT: ret i8* [[RET]]
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;
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%ret = call i8* @strchr(i8* %str, i32 %c)
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ret i8* %ret
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}
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