Accept 'inreg' attribute on x86 functions as

meaning sse_regparm (i.e. float/double values go
in XMM0 instead of ST0).  Update documentation
to reflect reality.

llvm-svn: 56619

2 files changed, 15 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
index b9f1aa45078..01f1f28b23e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
@@ -913,7 +913,8 @@ void SelectionDAGLowering::visitRet(ReturnInst &I) {
       MVT VT = ValueVTs[j];
 
       // FIXME: C calling convention requires the return type to be promoted to
-      // at least 32-bit. But this is not necessary for non-C calling conventions.
+      // at least 32-bit. But this is not necessary for non-C calling
+      // conventions.
       if (VT.isInteger()) {
         MVT MinVT = TLI.getRegisterType(MVT::i32);
         if (VT.bitsLT(MinVT))
@@ -934,9 +935,13 @@ void SelectionDAGLowering::visitRet(ReturnInst &I) {
       getCopyToParts(DAG, SDValue(RetOp.getNode(), RetOp.getResNo() + j),
                      &Parts[0], NumParts, PartVT, ExtendKind);
 
+      // 'inreg' on function refers to return value
+      ISD::ArgFlagsTy Flags = ISD::ArgFlagsTy();
+      if (F->paramHasAttr(0, ParamAttr::InReg))
+        Flags.setInReg();
       for (unsigned i = 0; i < NumParts; ++i) {
         NewValues.push_back(Parts[i]);
-        NewValues.push_back(DAG.getArgFlags(ISD::ArgFlagsTy()));
+        NewValues.push_back(DAG.getArgFlags(Flags));
       }
     }
   }
diff --git a/llvm/lib/Target/X86/X86CallingConv.td b/llvm/lib/Target/X86/X86CallingConv.td
index b98b5d9b495..590bc1015a9 100644
--- a/llvm/lib/Target/X86/X86CallingConv.td
+++ b/llvm/lib/Target/X86/X86CallingConv.td
@@ -43,10 +43,14 @@ def RetCC_X86Common : CallingConv<[
 
 // 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, ST1]>>,
-  CCIfType<[f64], CCAssignToReg<[ST0, ST1]>>,
+  // The X86-32 calling convention returns FP values in ST0, unless marked
+  // with "inreg" (used here to distinguish one kind of reg from another,
+  // weirdly; this is really the sse-regparm calling convention) in which
+  // case they use XMM0, otherwise it is the same as the common X86 calling
+  // conv.
+  CCIfInReg<CCIfSubtarget<"hasSSE2()", 
+    CCIfType<[f32, f64], CCAssignToReg<[XMM0,XMM1,XMM2]>>>>,
+  CCIfType<[f32,f64], CCAssignToReg<[ST0, ST1]>>,
   CCDelegateTo<RetCC_X86Common>
 ]>;