X86: Perform integer comparisons at i32 or larger.

[oota-llvm.git] / lib / Target / X86 / X86ISelLowering.cpp

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 6c8865915da9a8f24bc1b5342c15938ca16b79b1..df2785c06759ddf24b98ea7cfb7b98c31d0fabc3 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -3419,6 +3419,24 @@ bool X86::isCalleePop(CallingConv::ID CallingConv,
   }
 }
 
+/// \brief Return true if the condition is an unsigned comparison operation.
+static bool isX86CCUnsigned(unsigned X86CC) {
+  switch (X86CC) {
+  default: llvm_unreachable("Invalid integer condition!");
+  case X86::COND_E:     return true;
+  case X86::COND_G:     return false;
+  case X86::COND_GE:    return false;
+  case X86::COND_L:     return false;
+  case X86::COND_LE:    return false;
+  case X86::COND_NE:    return true;
+  case X86::COND_B:     return true;
+  case X86::COND_A:     return true;
+  case X86::COND_BE:    return true;
+  case X86::COND_AE:    return true;
+  }
+  llvm_unreachable("covered switch fell through?!");
+}
+
 /// TranslateX86CC - do a one to one translation of a ISD::CondCode to the X86
 /// specific condition code, returning the condition code and the LHS/RHS of the
 /// comparison to make.
@@ -9662,6 +9680,17 @@ SDValue X86TargetLowering::EmitCmp(SDValue Op0, SDValue Op1, unsigned X86CC,
   SDLoc dl(Op0);
   if ((Op0.getValueType() == MVT::i8 || Op0.getValueType() == MVT::i16 ||
        Op0.getValueType() == MVT::i32 || Op0.getValueType() == MVT::i64)) {
+    // Do the comparison at i32 if it's smaller. This avoids subregister
+    // aliasing issues. Keep the smaller reference if we're optimizing for
+    // size, however, as that'll allow better folding of memory operations.
+    if (Op0.getValueType() != MVT::i32 && Op0.getValueType() != MVT::i64 &&
+        !DAG.getMachineFunction().getFunction()->getAttributes().hasAttribute(
+             AttributeSet::FunctionIndex, Attribute::MinSize)) {
+      unsigned ExtendOp =
+          isX86CCUnsigned(X86CC) ? ISD::ZERO_EXTEND : ISD::SIGN_EXTEND;
+      Op0 = DAG.getNode(ExtendOp, dl, MVT::i32, Op0);
+      Op1 = DAG.getNode(ExtendOp, dl, MVT::i32, Op1);
+    }
     // Use SUB instead of CMP to enable CSE between SUB and CMP.
     SDVTList VTs = DAG.getVTList(Op0.getValueType(), MVT::i32);
     SDValue Sub = DAG.getNode(X86ISD::SUB, dl, VTs,