FIX PR 4459.

Not sure I understand how the temp register gets used,
but this fixes a bug and introduces no regressions.

llvm-svn: 74446

2 files changed, 16 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86FloatingPoint.cpp b/llvm/lib/Target/X86/X86FloatingPoint.cpp
index ed4eb444e9c..abacdb2f9b6 100644
--- a/llvm/lib/Target/X86/X86FloatingPoint.cpp
+++ b/llvm/lib/Target/X86/X86FloatingPoint.cpp
@@ -996,7 +996,7 @@ void FPS::handleSpecialFP(MachineBasicBlock::iterator &I) {
     // it is possible for FP0 to be alive after this instruction.
     if (!MI->killsRegister(X86::FP0)) {
       // Duplicate ST0
-      duplicateToTop(0, 0, I);
+      duplicateToTop(0, 7 /*temp register*/, I);
     }
     --StackTop;   // "Forget" we have something on the top of stack!
     break;
diff --git a/llvm/test/CodeGen/X86/inline-asm-fpstack3.ll b/llvm/test/CodeGen/X86/inline-asm-fpstack3.ll
new file mode 100644
index 00000000000..ac89a1d9ad5
--- /dev/null
+++ b/llvm/test/CodeGen/X86/inline-asm-fpstack3.ll
@@ -0,0 +1,15 @@
+; RUN: llvm-as < %s | llc -march=x86 > %t
+; RUN: grep {fld	%%st(0)} %t
+; PR4459
+
+declare x86_fp80 @ceil(x86_fp80)
+
+declare void @test(x86_fp80)
+
+define void @test2(x86_fp80 %a) {
+entry:
+	%0 = call x86_fp80 @ceil(x86_fp80 %a)
+	call void asm sideeffect "fistpl $0", "{st}"( x86_fp80 %0)
+	call void @test(x86_fp80 %0 )
+        ret void
+}