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 da2175bbd43c7deed82d399b3e60d3a95b5e7d57..4597a82473809f843f19fae39e78451d70f8acbb 100644 (file)
--- 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 da2175bbd43c7deed82d399b3e60d3a95b5e7d57..4597a82473809f843f19fae39e78451d70f8acbb 100644 (file)
--- 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();