From 5d52135a14da7ed417122b65e5493d9f15f2423c Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 29 Nov 2006 01:48:01 +0000
Subject: [PATCH] Upgrade the ugly darwin 64-bit bswap idiom (bswap %eax /
 bswap %edx / 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
---
 lib/Target/X86/X86TargetAsmInfo.cpp | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/lib/Target/X86/X86TargetAsmInfo.cpp b/lib/Target/X86/X86TargetAsmInfo.cpp
index 32d918efec1..4d44b7d591e 100644
--- a/lib/Target/X86/X86TargetAsmInfo.cpp
+++ b/lib/Target/X86/X86TargetAsmInfo.cpp
@@ -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;
 }