From: Chris Lattner <sabre@nondot.org>
Date: Fri, 7 May 2004 19:55:55 +0000 (+0000)
Subject: Make comparisons against the null pointer as efficient as integer comparisons
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=260195d2b1a2a3be54d932ccd8da45346bec5676;p=oota-llvm.git

Make comparisons against the null pointer as efficient as integer comparisons
against zero.  In particular, don't emit:

        mov %ESI, 0
        cmp %ECX, %ESI

instead, emit:

       test %ECX, %ECX


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13407 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/InstSelectSimple.cpp b/lib/Target/X86/InstSelectSimple.cpp
index da2175bbd43..4597a824738 100644
--- a/lib/Target/X86/InstSelectSimple.cpp
+++ b/lib/Target/X86/InstSelectSimple.cpp
@@ -829,7 +829,14 @@ unsigned ISel::EmitComparison(unsigned OpNum, Value *Op0, Value *Op1,
   unsigned Op0r = getReg(Op0, MBB, IP);
 
   // Special case handling of: cmp R, i
-  if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
+  if (isa<ConstantPointerNull>(Op1)) {
+    if (OpNum < 2)    // seteq/setne -> test
+      BuildMI(*MBB, IP, X86::TEST32rr, 2).addReg(Op0r).addReg(Op0r);
+    else
+      BuildMI(*MBB, IP, X86::CMP32ri, 2).addReg(Op0r).addImm(0);
+    return OpNum;
+
+  } else if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
     if (Class == cByte || Class == cShort || Class == cInt) {
       unsigned Op1v = CI->getRawValue();
 
diff --git a/lib/Target/X86/X86ISelSimple.cpp b/lib/Target/X86/X86ISelSimple.cpp
index da2175bbd43..4597a824738 100644
--- a/lib/Target/X86/X86ISelSimple.cpp
+++ b/lib/Target/X86/X86ISelSimple.cpp
@@ -829,7 +829,14 @@ unsigned ISel::EmitComparison(unsigned OpNum, Value *Op0, Value *Op1,
   unsigned Op0r = getReg(Op0, MBB, IP);
 
   // Special case handling of: cmp R, i
-  if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
+  if (isa<ConstantPointerNull>(Op1)) {
+    if (OpNum < 2)    // seteq/setne -> test
+      BuildMI(*MBB, IP, X86::TEST32rr, 2).addReg(Op0r).addReg(Op0r);
+    else
+      BuildMI(*MBB, IP, X86::CMP32ri, 2).addReg(Op0r).addImm(0);
+    return OpNum;
+
+  } else if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
     if (Class == cByte || Class == cShort || Class == cInt) {
       unsigned Op1v = CI->getRawValue();