On PowerPC64, integer return values (as well as arguments) are supposed

to be extended to a full register.   This is modeled in the IR by marking
the return value (or argument) with a signext or zeroext attribute.

However, while these attributes are respected for function arguments,
they are currently ignored for function return values by the PowerPC
back-end.  This patch updates PPCCallingConv.td to ask for the promotion
to i64, and fixes LowerReturn and LowerCallResult to implement it.

The new test case verifies that both arguments and return values are
properly extended when passing them; and also that the optimizers
understand incoming argument and return values are in fact guaranteed
by the ABI to be extended.

The patch caused a spurious breakage in CodeGen/PowerPC/coalesce-ext.ll,
since the test case used a "ret" instruction to create a use of an i32
value at the end of the function (to set up data flow as required for
what the test is intended to test).  Since there's now an implicit
promotion to i64, that data flow no longer works as expected.  To fix
this, this patch now adds an extra "add" to ensure we have an appropriate
use of the i32 value.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167396 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 50 insertions, 7 deletions

diff --git a/lib/Target/PowerPC/PPCCallingConv.td b/lib/Target/PowerPC/PPCCallingConv.td
index b2b5364856..3f87e883b1 100644
--- a/lib/Target/PowerPC/PPCCallingConv.td
+++ b/lib/Target/PowerPC/PPCCallingConv.td
@@ -12,12 +12,19 @@
 //
 //===----------------------------------------------------------------------===//
 
+/// CCIfSubtarget - Match if the current subtarget has a feature F.
+class CCIfSubtarget<string F, CCAction A>
+ : CCIf<!strconcat("State.getTarget().getSubtarget<PPCSubtarget>().", F), A>;
+
 //===----------------------------------------------------------------------===//
 // Return Value Calling Convention
 //===----------------------------------------------------------------------===//
 
 // Return-value convention for PowerPC
 def RetCC_PPC : CallingConv<[
+  // On PPC64, integer return values are always promoted to i64
+  CCIfType<[i32], CCIfSubtarget<"isPPC64()", CCPromoteToType<i64>>>,
+
   CCIfType<[i32], CCAssignToReg<[R3, R4, R5, R6, R7, R8, R9, R10]>>,
   CCIfType<[i64], CCAssignToReg<[X3, X4, X5, X6]>>,
   
diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index cda7e8cdc1..adf78d5233 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -3177,12 +3177,32 @@ PPCTargetLowering::LowerCallResult(SDValue Chain, SDValue InFlag,
   // Copy all of the result registers out of their specified physreg.
   for (unsigned i = 0, e = RVLocs.size(); i != e; ++i) {
     CCValAssign &VA = RVLocs[i];
-    EVT VT = VA.getValVT();
     assert(VA.isRegLoc() && "Can only return in registers!");
-    Chain = DAG.getCopyFromReg(Chain, dl,
-                               VA.getLocReg(), VT, InFlag).getValue(1);
-    InVals.push_back(Chain.getValue(0));
-    InFlag = Chain.getValue(2);
+
+    SDValue Val = DAG.getCopyFromReg(Chain, dl,
+                                     VA.getLocReg(), VA.getLocVT(), InFlag);
+    Chain = Val.getValue(1);
+    InFlag = Val.getValue(2);
+
+    switch (VA.getLocInfo()) {
+    default: llvm_unreachable("Unknown loc info!");
+    case CCValAssign::Full: break;
+    case CCValAssign::AExt:
+      Val = DAG.getNode(ISD::TRUNCATE, dl, VA.getValVT(), Val);
+      break;
+    case CCValAssign::ZExt:
+      Val = DAG.getNode(ISD::AssertZext, dl, VA.getLocVT(), Val,
+                        DAG.getValueType(VA.getValVT()));
+      Val = DAG.getNode(ISD::TRUNCATE, dl, VA.getValVT(), Val);
+      break;
+    case CCValAssign::SExt:
+      Val = DAG.getNode(ISD::AssertSext, dl, VA.getLocVT(), Val,
+                        DAG.getValueType(VA.getValVT()));
+      Val = DAG.getNode(ISD::TRUNCATE, dl, VA.getValVT(), Val);
+      break;
+    }
+
+    InVals.push_back(Val);
   }
 
   return Chain;
@@ -4316,8 +4336,24 @@ PPCTargetLowering::LowerReturn(SDValue Chain,
   for (unsigned i = 0; i != RVLocs.size(); ++i) {
     CCValAssign &VA = RVLocs[i];
     assert(VA.isRegLoc() && "Can only return in registers!");
-    Chain = DAG.getCopyToReg(Chain, dl, VA.getLocReg(),
-                             OutVals[i], Flag);
+
+    SDValue Arg = OutVals[i];
+
+    switch (VA.getLocInfo()) {
+    default: llvm_unreachable("Unknown loc info!");
+    case CCValAssign::Full: break;
+    case CCValAssign::AExt:
+      Arg = DAG.getNode(ISD::ANY_EXTEND, dl, VA.getLocVT(), Arg);
+      break;
+    case CCValAssign::ZExt:
+      Arg = DAG.getNode(ISD::ZERO_EXTEND, dl, VA.getLocVT(), Arg);
+      break;
+    case CCValAssign::SExt:
+      Arg = DAG.getNode(ISD::SIGN_EXTEND, dl, VA.getLocVT(), Arg);
+      break;
+    }
+
+    Chain = DAG.getCopyToReg(Chain, dl, VA.getLocReg(), Arg, Flag);
     Flag = Chain.getValue(1);
   }