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SimplifyLibCalls: Add basic optimization of memchr calls.

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This is just memchr(x, y, 0) -> nullptr and constant folding.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232896 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2015-03-21 15:36:21 +00:00
parent 046c58a3ee
commit 4b74df7229
4 changed files with 168 additions and 3 deletions
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9
include/llvm/ADT/StringRef.h
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@ -238,9 +238,12 @@ namespace llvm {
/// \returns The index of the first occurrence of \p C, or npos if not
/// found.
size_t find(char C, size_t From = 0) const {
for (size_t i = std::min(From, Length), e = Length; i != e; ++i)
if (Data[i] == C)
return i;
if (Length != 0) {
size_t FindBegin = std::min(From, Length);
if (const void *Found =
std::memchr(Data + FindBegin, C, Length - FindBegin))
return static_cast<const char *>(Found) - Data;
}
return npos;
}

1
include/llvm/Transforms/Utils/SimplifyLibCalls.h
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@ -116,6 +116,7 @@ private:
Value *optimizeStrSpn(CallInst *CI, IRBuilder<> &B);
Value *optimizeStrCSpn(CallInst *CI, IRBuilder<> &B);
Value *optimizeStrStr(CallInst *CI, IRBuilder<> &B);
Value *optimizeMemChr(CallInst *CI, IRBuilder<> &B);
Value *optimizeMemCmp(CallInst *CI, IRBuilder<> &B);
Value *optimizeMemCpy(CallInst *CI, IRBuilder<> &B);
Value *optimizeMemMove(CallInst *CI, IRBuilder<> &B);

40
lib/Transforms/Utils/SimplifyLibCalls.cpp
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@ -745,6 +745,44 @@ Value *LibCallSimplifier::optimizeStrStr(CallInst *CI, IRBuilder<> &B) {
return nullptr;
}
Value *LibCallSimplifier::optimizeMemChr(CallInst *CI, IRBuilder<> &B) {
Function *Callee = CI->getCalledFunction();
FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 3 || !FT->getParamType(0)->isPointerTy() ||
!FT->getParamType(1)->isIntegerTy(32) ||
!FT->getParamType(2)->isIntegerTy() ||
!FT->getReturnType()->isPointerTy())
return nullptr;
Value *SrcStr = CI->getArgOperand(0);
ConstantInt *CharC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getArgOperand(2));
// memchr(x, y, 0) -> null
if (LenC && LenC->isNullValue())
return Constant::getNullValue(CI->getType());
// Check if all arguments are constants. If so, we can constant fold.
StringRef Str;
if (!CharC || !LenC ||
!getConstantStringInfo(SrcStr, Str, /*Offset=*/0,
/*TrimAtNul=*/false))
return nullptr;
// Truncate the string to LenC. If Str is smaller than LenC we will still only
// scan the string, as reading past the end of it is undefined and we can just
// return null if we don't find the char.
Str = Str.substr(0, LenC->getZExtValue());
// Compute the offset.
size_t I = Str.find(CharC->getSExtValue() & 0xFF);
if (I == StringRef::npos) // Didn't find the char. memchr returns null.
return Constant::getNullValue(CI->getType());
// memchr(s+n,c,l) -> gep(s+n+i,c)
return B.CreateGEP(SrcStr, B.getInt64(I), "memchr");
}
Value *LibCallSimplifier::optimizeMemCmp(CallInst *CI, IRBuilder<> &B) {
Function *Callee = CI->getCalledFunction();
FunctionType *FT = Callee->getFunctionType();
@ -1852,6 +1890,8 @@ Value *LibCallSimplifier::optimizeStringMemoryLibCall(CallInst *CI,
return optimizeStrCSpn(CI, Builder);
case LibFunc::strstr:
return optimizeStrStr(CI, Builder);
case LibFunc::memchr:
return optimizeMemChr(CI, Builder);
case LibFunc::memcmp:
return optimizeMemCmp(CI, Builder);
case LibFunc::memcpy:

121
test/Transforms/InstCombine/memchr.ll Normal file
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@ -0,0 +1,121 @@
; Test that the memchr library call simplifier works correctly.
; RUN: opt < %s -instcombine -S | FileCheck %s
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"
@hello = constant [14 x i8] c"hello world\5Cn\00"
@hellonull = constant [14 x i8] c"hello\00world\5Cn\00"
@null = constant [1 x i8] zeroinitializer
@chp = global i8* zeroinitializer
declare i8* @memchr(i8*, i32, i32)
define void @test1() {
; CHECK-LABEL: @test1
; CHECK: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 6)
; CHECK-NOT: call i8* @memchr
; CHECK: ret void
%str = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
%dst = call i8* @memchr(i8* %str, i32 119, i32 14)
store i8* %dst, i8** @chp
ret void
}
define void @test2() {
; CHECK-LABEL: @test2
; CHECK: store i8* null, i8** @chp, align 4
; CHECK-NOT: call i8* @memchr
; CHECK: ret void
%str = getelementptr [1 x i8], [1 x i8]* @null, i32 0, i32 0
%dst = call i8* @memchr(i8* %str, i32 119, i32 1)
store i8* %dst, i8** @chp
ret void
}
define void @test3() {
; CHECK-LABEL: @test3
; CHECK: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 13)
; CHECK-NOT: call i8* @memchr
; CHECK: ret void
%src = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
%dst = call i8* @memchr(i8* %src, i32 0, i32 14)
store i8* %dst, i8** @chp
ret void
}
define void @test4(i32 %chr) {
; CHECK-LABEL: @test4
; CHECK: call i8* @memchr
; CHECK-NOT: call i8* @memchr
; CHECK: ret void
%src = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
%dst = call i8* @memchr(i8* %src, i32 %chr, i32 14)
store i8* %dst, i8** @chp
ret void
}
define void @test5() {
; CHECK-LABEL: @test5
; CHECK: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 13)
; CHECK-NOT: call i8* @memchr
; CHECK: ret void
%src = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
%dst = call i8* @memchr(i8* %src, i32 65280, i32 14)
store i8* %dst, i8** @chp
ret void
}
define void @test6() {
; CHECK-LABEL: @test6
; CHECK: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hello, i32 0, i32 6)
; CHECK-NOT: call i8* @memchr
; CHECK: ret void
%src = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
; Overflow, but we still find the right thing.
%dst = call i8* @memchr(i8* %src, i32 119, i32 100)
store i8* %dst, i8** @chp
ret void
}
define void @test7() {
; CHECK-LABEL: @test7
; CHECK: store i8* null, i8** @chp, align 4
; CHECK-NOT: call i8* @memchr
; CHECK: ret void
%src = getelementptr [14 x i8], [14 x i8]* @hello, i32 0, i32 0
; Overflow
%dst = call i8* @memchr(i8* %src, i32 120, i32 100)
store i8* %dst, i8** @chp
ret void
}
define void @test8() {
; CHECK-LABEL: @test8
; CHECK: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hellonull, i32 0, i32 6)
; CHECK-NOT: call i8* @memchr
; CHECK: ret void
%str = getelementptr [14 x i8], [14 x i8]* @hellonull, i32 0, i32 0
%dst = call i8* @memchr(i8* %str, i32 119, i32 14)
store i8* %dst, i8** @chp
ret void
}
define void @test9() {
; CHECK-LABEL: @test9
; CHECK: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @hellonull, i32 0, i32 6)
; CHECK-NOT: call i8* @memchr
; CHECK: ret void
%str = getelementptr [14 x i8], [14 x i8]* @hellonull, i32 0, i32 2
%dst = call i8* @memchr(i8* %str, i32 119, i32 12)
store i8* %dst, i8** @chp
ret void
}