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Turn strcmp into memcmp, such as strcmp(P, "x") --> memcmp(P, "x", 2).

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61297 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky
2008-12-21 00:19:21 +00:00
parent b12b1a27f5
commit 13a09e298c
2 changed files with 40 additions and 2 deletions
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28
lib/Transforms/Scalar/SimplifyLibCalls.cpp
View File

@@ -81,6 +81,9 @@ public:
/// a pointer, Val is an i32 value, and Len is an 'intptr_t' value. /// a pointer, Val is an i32 value, and Len is an 'intptr_t' value.
Value *EmitMemChr(Value *Ptr, Value *Val, Value *Len, IRBuilder<> &B); Value *EmitMemChr(Value *Ptr, Value *Val, Value *Len, IRBuilder<> &B);
/// EmitMemCmp - Emit a call to the memcmp function.
Value *EmitMemCmp(Value *Ptr1, Value *Ptr2, Value *Len, IRBuilder<> &B);
/// EmitUnaryFloatFnCall - Emit a call to the unary function named 'Name' (e.g. /// EmitUnaryFloatFnCall - Emit a call to the unary function named 'Name' (e.g.
/// 'floor'). This function is known to take a single of type matching 'Op' /// 'floor'). This function is known to take a single of type matching 'Op'
/// and returns one value with the same type. If 'Op' is a long double, 'l' /// and returns one value with the same type. If 'Op' is a long double, 'l'
@@ -151,6 +154,19 @@ Value *LibCallOptimization::EmitMemChr(Value *Ptr, Value *Val,
return B.CreateCall3(MemChr, CastToCStr(Ptr, B), Val, Len, "memchr"); return B.CreateCall3(MemChr, CastToCStr(Ptr, B), Val, Len, "memchr");
} }
/// EmitMemCmp - Emit a call to the memcmp function.
Value *LibCallOptimization::EmitMemCmp(Value *Ptr1, Value *Ptr2,
Value *Len, IRBuilder<> &B) {
Module *M = Caller->getParent();
Value *MemCmp = M->getOrInsertFunction("memcmp",
Type::Int32Ty,
PointerType::getUnqual(Type::Int8Ty),
PointerType::getUnqual(Type::Int8Ty),
TD->getIntPtrType(), NULL);
return B.CreateCall3(MemCmp, CastToCStr(Ptr1, B), CastToCStr(Ptr2, B),
Len, "memcmp");
}
/// EmitUnaryFloatFnCall - Emit a call to the unary function named 'Name' (e.g. /// EmitUnaryFloatFnCall - Emit a call to the unary function named 'Name' (e.g.
/// 'floor'). This function is known to take a single of type matching 'Op' and /// 'floor'). This function is known to take a single of type matching 'Op' and
/// returns one value with the same type. If 'Op' is a long double, 'l' is /// returns one value with the same type. If 'Op' is a long double, 'l' is
@@ -537,6 +553,18 @@ struct VISIBILITY_HIDDEN StrCmpOpt : public LibCallOptimization {
// strcmp(x, y) -> cnst (if both x and y are constant strings) // strcmp(x, y) -> cnst (if both x and y are constant strings)
if (HasStr1 && HasStr2) if (HasStr1 && HasStr2)
return ConstantInt::get(CI->getType(), strcmp(Str1.c_str(),Str2.c_str())); return ConstantInt::get(CI->getType(), strcmp(Str1.c_str(),Str2.c_str()));
// strcmp(P, "x") -> memcmp(P, "x", 2)
uint64_t Len1 = GetStringLength(Str1P);
uint64_t Len2 = GetStringLength(Str2P);
if (Len1 || Len2) {
// Choose the smallest Len excluding 0 which means 'unknown'.
if (!Len1 || (Len2 && Len2 < Len1))
Len1 = Len2;
return EmitMemCmp(Str1P, Str2P,
ConstantInt::get(TD->getIntPtrType(), Len1), B);
}
return 0; return 0;
} }
}; };

10
test/Transforms/SimplifyLibCalls/2008-12-20-StrcmpMemcmp.ll Normal file
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@@ -0,0 +1,10 @@
; RUN: llvm-as < %s | opt -simplify-libcalls | llvm-dis | grep call.*memcmp
@.str = internal constant [2 x i8] c"x\00"
declare i32 @strcmp(i8* %dest, i8* %src)
define i32 @foo(i8* %x, i8* %y) {
%A = call i32 @strcmp(i8* %x, i8* getelementptr ([2 x i8]* @.str, i32 0, i32 0))
ret i32 %A
}