X86: Use btq for bit tests if the immediate can't be encoded in 32 bits.

Before:
	movabsq	$4294967296, %rax       ## encoding: [0x48,0xb8,0x00,0x00,0x00,0x00,0x01,0x00,0x00,0x00]
	testq	%rax, %rdi              ## encoding: [0x48,0x85,0xf8]
	jne	LBB0_2                  ## encoding: [0x75,A]

After:
	btq	$32, %rdi               ## encoding: [0x48,0x0f,0xba,0xe7,0x20]
	jb	LBB0_2                  ## encoding: [0x72,A]

btq is usually slower than testq because it doesn't fuse with the jump, but here we're better off
saving one register and a giant movabsq.

llvm-svn: 145103

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 7e35fd24a0b..213e880d968 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -8543,11 +8543,19 @@ SDValue X86TargetLowering::LowerToBT(SDValue And, ISD::CondCode CC,
       }
   } else if (Op1.getOpcode() == ISD::Constant) {
     ConstantSDNode *AndRHS = cast<ConstantSDNode>(Op1);
+    uint64_t AndRHSVal = AndRHS->getZExtValue();
     SDValue AndLHS = Op0;
-    if (AndRHS->getZExtValue() == 1 && AndLHS.getOpcode() == ISD::SRL) {
+
+    if (AndRHSVal == 1 && AndLHS.getOpcode() == ISD::SRL) {
       LHS = AndLHS.getOperand(0);
       RHS = AndLHS.getOperand(1);
     }
+
+    // Use BT if the immediate can't be encoded in a TEST instruction.
+    if (!isUInt<32>(AndRHSVal) && isPowerOf2_64(AndRHSVal)) {
+      LHS = AndLHS;
+      RHS = DAG.getConstant(Log2_64_Ceil(AndRHSVal), LHS.getValueType());
+    }
   }
 
   if (LHS.getNode()) {