Enhance boolean simplification to handle 16-/64-bit RDRAND

- RDRAND always clears the destination value when a random value is not
  available (i.e. CF == 0). This value is truncated or zero-extended as
  the false boolean value to be returned. Boolean simplification needs
  to skip this 'zext' or 'trunc' node.

llvm-svn: 178312

1 files changed, 9 insertions, 4 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 709e9e8aaee..e0f87c03b7c 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -15821,8 +15821,9 @@ static SDValue checkBoolTestSetCCCombine(SDValue Cmp, X86::CondCode &CC) {
     // Quit if the constant is neither 0 or 1.
     return SDValue();
 
-  // Skip 'zext' node.
-  if (SetCC.getOpcode() == ISD::ZERO_EXTEND)
+  // Skip 'zext' or 'trunc' node.
+  if (SetCC.getOpcode() == ISD::ZERO_EXTEND ||
+      SetCC.getOpcode() == ISD::TRUNCATE)
     SetCC = SetCC.getOperand(0);
 
   switch (SetCC.getOpcode()) {
@@ -15841,9 +15842,13 @@ static SDValue checkBoolTestSetCCCombine(SDValue Cmp, X86::CondCode &CC) {
       return SDValue();
     // Quit if false value is not a constant.
     if (!FVal) {
-      // A special case for rdrand, where 0 is set if false cond is found.
       SDValue Op = SetCC.getOperand(0);
-      if (Op.getOpcode() != X86ISD::RDRAND)
+      // Skip 'zext' or 'trunc' node.
+      if (Op.getOpcode() == ISD::ZERO_EXTEND ||
+          Op.getOpcode() == ISD::TRUNCATE)
+        Op = Op.getOperand(0);
+      // A special case for rdrand, where 0 is set if false cond is found.
+      if (Op.getOpcode() != X86ISD::RDRAND || Op.getResNo() != 0)
         return SDValue();
     }
     // Quit if false value is not the constant 0 or 1.