[SystemZ] Assign the full space for promoted and split outgoing args.

When a large "irregular" (e.g. i96) integer call argument is converted to
indirect, 64-bit parts are stored to the stack. The full stack space
(e.g. i128) was not allocated prior to this patch, but rather just the exact
space of the original type. This caused neighboring values on the stack to be
overwritten.

Thanks to Josh Stone for reporting this.

Review: Ulrich Weigand
Fixes https://bugs.llvm.org/show_bug.cgi?id=49322
Differential Revision: https://reviews.llvm.org/D97514

llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

@@ -1547,6 +1547,7 @@ SystemZTargetLowering::LowerCall(CallLoweringInfo &CLI,
   bool IsVarArg = CLI.IsVarArg;
   MachineFunction &MF = DAG.getMachineFunction();
   EVT PtrVT = getPointerTy(MF.getDataLayout());
+  LLVMContext &Ctx = *DAG.getContext();
 
   // Detect unsupported vector argument and return types.
   if (Subtarget.hasVector()) {
@@ -1556,7 +1557,7 @@ SystemZTargetLowering::LowerCall(CallLoweringInfo &CLI,
 
   // Analyze the operands of the call, assigning locations to each operand.
   SmallVector<CCValAssign, 16> ArgLocs;
-  SystemZCCState ArgCCInfo(CallConv, IsVarArg, MF, ArgLocs, *DAG.getContext());
+  SystemZCCState ArgCCInfo(CallConv, IsVarArg, MF, ArgLocs, Ctx);
   ArgCCInfo.AnalyzeCallOperands(Outs, CC_SystemZ);
 
   // We don't support GuaranteedTailCallOpt, only automatically-detected
@@ -1581,14 +1582,25 @@ SystemZTargetLowering::LowerCall(CallLoweringInfo &CLI,
 
     if (VA.getLocInfo() == CCValAssign::Indirect) {
       // Store the argument in a stack slot and pass its address.
-      SDValue SpillSlot = DAG.CreateStackTemporary(Outs[I].ArgVT);
+      unsigned ArgIndex = Outs[I].OrigArgIndex;
+      EVT SlotVT;
+      if (I + 1 != E && Outs[I + 1].OrigArgIndex == ArgIndex) {
+        // Allocate the full stack space for a promoted (and split) argument.
+        Type *OrigArgType = CLI.Args[Outs[I].OrigArgIndex].Ty;
+        EVT OrigArgVT = getValueType(MF.getDataLayout(), OrigArgType);
+        MVT PartVT = getRegisterTypeForCallingConv(Ctx, CLI.CallConv, OrigArgVT);
+        unsigned N = getNumRegistersForCallingConv(Ctx, CLI.CallConv, OrigArgVT);
+        SlotVT = EVT::getIntegerVT(Ctx, PartVT.getSizeInBits() * N);
+      } else {
+        SlotVT = Outs[I].ArgVT;
+      }
+      SDValue SpillSlot = DAG.CreateStackTemporary(SlotVT);
       int FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();
       MemOpChains.push_back(
           DAG.getStore(Chain, DL, ArgValue, SpillSlot,
                        MachinePointerInfo::getFixedStack(MF, FI)));
       // If the original argument was split (e.g. i128), we need
       // to store all parts of it here (and pass just one address).
-      unsigned ArgIndex = Outs[I].OrigArgIndex;
       assert (Outs[I].PartOffset == 0);
       while (I + 1 != E && Outs[I + 1].OrigArgIndex == ArgIndex) {
         SDValue PartValue = OutVals[I + 1];
@@ -1598,6 +1610,8 @@ SystemZTargetLowering::LowerCall(CallLoweringInfo &CLI,
         MemOpChains.push_back(
             DAG.getStore(Chain, DL, PartValue, Address,
                          MachinePointerInfo::getFixedStack(MF, FI)));
+        assert((PartOffset + PartValue.getValueType().getStoreSize() <=
+                SlotVT.getStoreSize()) && "Not enough space for argument part!");
         ++I;
       }
       ArgValue = SpillSlot;
@@ -1691,7 +1705,7 @@ SystemZTargetLowering::LowerCall(CallLoweringInfo &CLI,
 
   // Assign locations to each value returned by this call.
   SmallVector<CCValAssign, 16> RetLocs;
-  CCState RetCCInfo(CallConv, IsVarArg, MF, RetLocs, *DAG.getContext());
+  CCState RetCCInfo(CallConv, IsVarArg, MF, RetLocs, Ctx);
   RetCCInfo.AnalyzeCallResult(Ins, RetCC_SystemZ);
 
   // Copy all of the result registers out of their specified physreg.

llvm/test/CodeGen/SystemZ/args-11.ll

@@ -0,0 +1,54 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; Test outgoing promoted arguments that are split (and passed by reference).
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
+
+; The i96 arg is promoted to i128 and should get the full stack space.
+declare void @fn1(i96)
+define i32 @fn2() {
+; CHECK-LABEL: fn2:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    stmg %r14, %r15, 112(%r15)
+; CHECK-NEXT:    .cfi_offset %r14, -48
+; CHECK-NEXT:    .cfi_offset %r15, -40
+; CHECK-NEXT:    aghi %r15, -184
+; CHECK-NEXT:    .cfi_def_cfa_offset 344
+; CHECK-NEXT:    mvhi 180(%r15), -1
+; CHECK-NEXT:    mvghi 168(%r15), 0
+; CHECK-NEXT:    la %r2, 160(%r15)
+; CHECK-NEXT:    mvghi 160(%r15), 0
+; CHECK-NEXT:    brasl %r14, fn1@PLT
+; CHECK-NEXT:    l %r2, 180(%r15)
+; CHECK-NEXT:    lmg %r14, %r15, 296(%r15)
+; CHECK-NEXT:    br %r14
+  %1 = alloca i32
+  store i32 -1, i32* %1
+  call void @fn1(i96 0)
+  %2 = load i32, i32* %1
+  ret i32 %2
+}
+
+declare void @fn3(i136)
+define i32 @fn4() {
+; CHECK-LABEL: fn4:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    stmg %r14, %r15, 112(%r15)
+; CHECK-NEXT:    .cfi_offset %r14, -48
+; CHECK-NEXT:    .cfi_offset %r15, -40
+; CHECK-NEXT:    aghi %r15, -192
+; CHECK-NEXT:    .cfi_def_cfa_offset 352
+; CHECK-NEXT:    mvhi 188(%r15), -1
+; CHECK-NEXT:    mvghi 176(%r15), 0
+; CHECK-NEXT:    mvghi 168(%r15), 0
+; CHECK-NEXT:    la %r2, 160(%r15)
+; CHECK-NEXT:    mvghi 160(%r15), 0
+; CHECK-NEXT:    brasl %r14, fn3@PLT
+; CHECK-NEXT:    l %r2, 188(%r15)
+; CHECK-NEXT:    lmg %r14, %r15, 304(%r15)
+; CHECK-NEXT:    br %r14
+  %1 = alloca i32
+  store i32 -1, i32* %1
+  call void @fn3(i136 0)
+  %2 = load i32, i32* %1
+  ret i32 %2
+}