Fix PR4484.

This was caused by me confounding FP0 and ST(0).

llvm-svn: 74523

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86FloatingPoint.cpp b/llvm/lib/Target/X86/X86FloatingPoint.cpp
index abacdb2f9b6..c282dc00947 100644
--- a/llvm/lib/Target/X86/X86FloatingPoint.cpp
+++ b/llvm/lib/Target/X86/X86FloatingPoint.cpp
@@ -990,16 +990,18 @@ void FPS::handleSpecialFP(MachineBasicBlock::iterator &I) {
   }
   case X86::FpSET_ST0_32:
   case X86::FpSET_ST0_64:
-  case X86::FpSET_ST0_80:
+  case X86::FpSET_ST0_80: {
+    unsigned RegOnTop = getStackEntry(0);
     // FpSET_ST0_80 is generated by copyRegToReg for both function return
     // and inline assembly with the "st" constrain. In the latter case,
-    // it is possible for FP0 to be alive after this instruction.
-    if (!MI->killsRegister(X86::FP0)) {
+    // it is possible for ST(0) to be alive after this instruction.
+    if (!MI->killsRegister(X86::FP0 + RegOnTop)) {
       // Duplicate ST0
       duplicateToTop(0, 7 /*temp register*/, I);
     }
     --StackTop;   // "Forget" we have something on the top of stack!
     break;
+  }
   case X86::FpSET_ST1_32:
   case X86::FpSET_ST1_64:
   case X86::FpSET_ST1_80: