For fastcc on x86, let ECX be used as a return register after EAX and EDX

llvm-svn: 91410

2 files changed, 23 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86CallingConv.td b/llvm/lib/Target/X86/X86CallingConv.td
index d77f0390b10..12d3d04eb6b 100644
--- a/llvm/lib/Target/X86/X86CallingConv.td
+++ b/llvm/lib/Target/X86/X86CallingConv.td
@@ -64,11 +64,18 @@ def RetCC_X86_32_C : CallingConv<[
 // X86-32 FastCC return-value convention.
 def RetCC_X86_32_Fast : CallingConv<[
   // The X86-32 fastcc returns 1, 2, or 3 FP values in XMM0-2 if the target has
-  // SSE2, otherwise it is the the C calling conventions.
+  // SSE2.
   // This can happen when a float, 2 x float, or 3 x float vector is split by
   // target lowering, and is returned in 1-3 sse regs.
   CCIfType<[f32], CCIfSubtarget<"hasSSE2()", CCAssignToReg<[XMM0,XMM1,XMM2]>>>,
   CCIfType<[f64], CCIfSubtarget<"hasSSE2()", CCAssignToReg<[XMM0,XMM1,XMM2]>>>,
+
+  // For integers, ECX can be used as an extra return register
+  CCIfType<[i8],  CCAssignToReg<[AL, DL, CL]>>,
+  CCIfType<[i16], CCAssignToReg<[AX, DX, CX]>>,
+  CCIfType<[i32], CCAssignToReg<[EAX, EDX, ECX]>>,
+
+  // Otherwise, it is the same as the common X86 calling convention.
   CCDelegateTo<RetCC_X86Common>
 ]>;
 
diff --git a/llvm/test/CodeGen/X86/fastcc3struct.ll b/llvm/test/CodeGen/X86/fastcc3struct.ll
new file mode 100644
index 00000000000..84f8ef6cf36
--- /dev/null
+++ b/llvm/test/CodeGen/X86/fastcc3struct.ll
@@ -0,0 +1,15 @@
+; RUN: llc < %s -march=x86 -o %t
+; RUN: grep "movl	.48, %ecx" %t
+; RUN: grep "movl	.24, %edx" %t
+; RUN: grep "movl	.12, %eax" %t
+
+%0 = type { i32, i32, i32 }
+
+define internal fastcc %0 @ReturnBigStruct() nounwind readnone {
+entry:
+  %0 = insertvalue %0 zeroinitializer, i32 12, 0
+  %1 = insertvalue %0 %0, i32 24, 1
+  %2 = insertvalue %0 %1, i32 48, 2
+  ret %0 %2
+}
+