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Upgrade the ugly darwin 64-bit bswap idiom (bswap %eax / bswap %edx /

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xchgl %eax, %edx) to llvm.bswap.i64.  This compiles:

long long test2(long long A) {
  return _OSSwapInt64(A);
}

to:

_test2:
        movl 8(%esp), %eax
        movl 4(%esp), %edx
        bswapl %eax
        bswapl %edx
        ret

instead of:

_test2:
        movl 8(%esp), %edx
        movl 4(%esp), %eax
        bswap   %eax
        bswap   %edx
        xchgl   %eax, %edx
        ret

GCC manages (with -fomit-frame-pointer) the uglier:

_test2:
        subl    $4, %esp
        movl    8(%esp), %eax
        movl    12(%esp), %edx
        bswap   %eax
        bswap   %edx
        xchgl   %eax, %edx
        addl    $4, %esp
        ret


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32001 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-11-29 01:48:01 +00:00
parent a5a57d66f5
commit 5d52135a14
1 changed files with 23 additions and 1 deletions
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24
lib/Target/X86/X86TargetAsmInfo.cpp
View File

@ -199,7 +199,7 @@ bool X86TargetAsmInfo::LowerToBSwap(CallInst *CI) const {
bool X86TargetAsmInfo::ExpandInlineAsm(CallInst *CI) const {
InlineAsm *IA = cast<InlineAsm>(CI->getCalledValue());
//std::vector<InlineAsm::ConstraintInfo> Constraints = IA->ParseConstraints();
std::vector<InlineAsm::ConstraintInfo> Constraints = IA->ParseConstraints();
std::string AsmStr = IA->getAsmString();
@ -214,6 +214,7 @@ bool X86TargetAsmInfo::ExpandInlineAsm(CallInst *CI) const {
AsmPieces.clear();
SplitString(AsmStr, AsmPieces, " \t"); // Split with whitespace.
// bswap $0
if (AsmPieces.size() == 2 &&
AsmPieces[0] == "bswap" && AsmPieces[1] == "$0") {
// No need to check constraints, nothing other than the equivalent of
@ -221,6 +222,27 @@ bool X86TargetAsmInfo::ExpandInlineAsm(CallInst *CI) const {
return LowerToBSwap(CI);
}
break;
case 3:
if (CI->getType() == Type::ULongTy && Constraints.size() >= 2 &&
Constraints[0].Codes.size() == 1 && Constraints[0].Codes[0] == "A" &&
Constraints[1].Codes.size() == 1 && Constraints[1].Codes[0] == "0") {
// bswap %eax / bswap %edx / xchgl %eax, %edx -> llvm.bswap.i64
std::vector<std::string> Words;
SplitString(AsmPieces[0], Words, " \t");
if (Words.size() == 2 && Words[0] == "bswap" && Words[1] == "%eax") {
Words.clear();
SplitString(AsmPieces[1], Words, " \t");
if (Words.size() == 2 && Words[0] == "bswap" && Words[1] == "%edx") {
Words.clear();
SplitString(AsmPieces[2], Words, " \t,");
if (Words.size() == 3 && Words[0] == "xchgl" && Words[1] == "%eax" &&
Words[2] == "%edx") {
return LowerToBSwap(CI);
}
}
}
}
break;
}
return false;
}