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fd48a80e14
strchr("123!", C) != nullptr is a common pattern to check if C is one
of 1, 2, 3 or !. If the largest element of the string is smaller than
the target's register size we can easily create a bitfield and just
do a simple test for set membership.
int foo(char C) { return strchr("123!", C) != nullptr; } now becomes
cmpl $64, %edi ## range check
sbbb %al, %al
movabsq $0xE000200000001, %rcx
btq %rdi, %rcx ## bit test
sbbb %cl, %cl
andb %al, %cl ## and the two conditions
andb $1, %cl
movzbl %cl, %eax ## returning an int
ret
(imho the backend should expand this into a series of branches, but
that's a different story)
The code is currently limited to bit fields that fit in a register, so
usually 64 or 32 bits. Sadly, this misses anything using alpha chars
or {}. This could be fixed by just emitting a i128 bit field, but that
can generate really ugly code so we have to find a better way. To some
degree this is also recreating switch lowering logic, but we can't
simply emit a switch instruction and thus change the CFG within
instcombine.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232902 91177308-0d34-0410-b5e6-96231b3b80d8
96 lines
2.9 KiB
LLVM
96 lines
2.9 KiB
LLVM
; 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: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 6)
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; CHECK-NOT: call i8* @strchr
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; CHECK: ret void
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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: store i8* null, i8** @chp, align 4
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; CHECK-NOT: call i8* @strchr
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; CHECK: ret void
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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: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 13)
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; CHECK-NOT: call i8* @strchr
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; CHECK: ret void
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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: call i8* @memchr
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; CHECK-NOT: call i8* @strchr
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; CHECK: ret void
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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: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 13)
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; CHECK-NOT: call i8* @strchr
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; CHECK: ret void
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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: %strlen = call i32 @strlen(i8* %str)
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; CHECK-NOT: call i8* @strchr
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; CHECK: %strchr = getelementptr i8, i8* %str, i32 %strlen
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; CHECK: store i8* %strchr, i8** @chp, align 4
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; CHECK: ret void
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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: [[TRUNC:%.*]] = trunc i32 %C to i16
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; CHECK-NEXT: %memchr.bounds = icmp ult i16 [[TRUNC]], 16
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; CHECK-NEXT: [[SHL:%.*]] = shl i16 1, [[TRUNC]]
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; CHECK-NEXT: [[AND:%.*]] = and i16 [[SHL]], 9217
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; CHECK-NEXT: %memchr.bits = icmp ne i16 [[AND]], 0
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; CHECK-NEXT: %memchr1 = and i1 %memchr.bounds, %memchr.bits
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; CHECK-NEXT: ret i1 %memchr1
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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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