Enable support for returning two long-double values in ST(0)/ST(1).

This allows us to compile fp-stack-2results.ll into:

_test:
	fldz
	fld1
	ret

which returns 1 in ST(0) and 0 in ST(1).  This is needed for x86-64
_Complex long double.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48632 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 15 insertions, 7 deletions

diff --git a/lib/Target/X86/X86CallingConv.td b/lib/Target/X86/X86CallingConv.td
index 4f25f1f27a..70f18c5789 100644
--- a/lib/Target/X86/X86CallingConv.td
+++ b/lib/Target/X86/X86CallingConv.td
@@ -38,15 +38,15 @@ def RetCC_X86Common : CallingConv<[
   CCIfType<[v8i8, v4i16, v2i32, v1i64], CCAssignToReg<[MM0]>>,
 
   // Long double types are always returned in ST0 (even with SSE).
-  CCIfType<[f80], CCAssignToReg<[ST0]>>
+  CCIfType<[f80], CCAssignToReg<[ST0, ST1]>>
 ]>;
 
 // X86-32 C return-value convention.
 def RetCC_X86_32_C : CallingConv<[
   // The X86-32 calling convention returns FP values in ST0, otherwise it is the
   // same as the common X86 calling conv.
-  CCIfType<[f32], CCAssignToReg<[ST0]>>,
-  CCIfType<[f64], CCAssignToReg<[ST0]>>,
+  CCIfType<[f32], CCAssignToReg<[ST0, ST1]>>,
+  CCIfType<[f64], CCAssignToReg<[ST0, ST1]>>,
   CCDelegateTo<RetCC_X86Common>
 ]>;
 
diff --git a/lib/Target/X86/X86FloatingPoint.cpp b/lib/Target/X86/X86FloatingPoint.cpp
index ca965375f2..d9ab1ed415 100644
--- a/lib/Target/X86/X86FloatingPoint.cpp
+++ b/lib/Target/X86/X86FloatingPoint.cpp
@@ -1053,9 +1053,6 @@ void FPS::handleSpecialFP(MachineBasicBlock::iterator &I) {
       return;
     }
     
-    assert(0 && "TODO: This code should work, but has never been tested."
-           "Test it when we have multiple FP return values working");
-    
     // Otherwise, we are returning two values:
     // 2) If returning the same value for both, we only have one thing in the FP
     //    stack.  Consider:  RET FP1, FP1
@@ -1083,7 +1080,7 @@ void FPS::handleSpecialFP(MachineBasicBlock::iterator &I) {
     /// 4) Finally, FirstFPRegOp must be in ST(0) and SecondFPRegOp must be in
     /// ST(1).  Just remove both from our understanding of the stack and return.
     assert(getStackEntry(0) == FirstFPRegOp && "Unknown regs live");
-    assert(getStackEntry(0) == SecondFPRegOp && "Unknown regs live");
+    assert(getStackEntry(1) == SecondFPRegOp && "Unknown regs live");
     StackTop = 0;
     return;
   }
diff --git a/test/CodeGen/X86/fp-stack-2results.ll b/test/CodeGen/X86/fp-stack-2results.ll
new file mode 100644
index 0000000000..b44d3dd511
--- /dev/null
+++ b/test/CodeGen/X86/fp-stack-2results.ll
@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep fldz
+; RUN: llvm-as < %s | llc -march=x86-64 | grep fld1
+
+; This is basically this code on x86-64:
+; _Complex long double test() { return 1.0; }
+define {x86_fp80, x86_fp80} @test() {
+  %A = fpext double 1.0 to x86_fp80
+  %B = fpext double 0.0 to x86_fp80
+  ret x86_fp80 %A, x86_fp80 %B
+}
+