[X86] Preserve BasePtr for LEA64_32r

When replacing FrameIndex with BasePtr, we must preserve BasePtr for
LEA64_32r since BasePtr is used later for stack adjustment if it is
the same as StackPtr.

Patch by H.J Lu <hjl.tools@gmail.com>

Differential Revision: https://reviews.llvm.org/D23575

llvm-svn: 283486

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index 5a33b5defde..4401d1769ba 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp
@@ -669,12 +669,14 @@ X86RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
   // For LEA64_32r when BasePtr is 32-bits (X32) we can use full-size 64-bit
   // register as source operand, semantic is the same and destination is
   // 32-bits. It saves one byte per lea in code since 0x67 prefix is avoided.
+  // Don't change BasePtr since it is used later for stack adjustment.
+  unsigned MachineBasePtr = BasePtr;
   if (Opc == X86::LEA64_32r && X86::GR32RegClass.contains(BasePtr))
-    BasePtr = getX86SubSuperRegister(BasePtr, 64);
+    MachineBasePtr = getX86SubSuperRegister(BasePtr, 64);
 
   // This must be part of a four operand memory reference.  Replace the
-  // FrameIndex with base register with EBP.  Add an offset to the offset.
-  MI.getOperand(FIOperandNum).ChangeToRegister(BasePtr, false);
+  // FrameIndex with base register.  Add an offset to the offset.
+  MI.getOperand(FIOperandNum).ChangeToRegister(MachineBasePtr, false);
 
   // Now add the frame object offset to the offset from EBP.
   int FIOffset;