[SystemZ] Improve handling of "packed-stack" function attribute.

[jonpa]

Summary

Instead of just calling hasFnAttribute(), call getFnAttribute() and check that it is set to "true".

It seems that the "backchain" attribute does not have to be checked this way, since it is simply present or non-present. Would this be preferrable perhaps also for "packed-stack" (instead of this patch)?

[uweigand]

It seems that the "backchain" attribute does not have to be checked this way, since it is simply present or non-present. Would this be preferrable perhaps also for "packed-stack" (instead of this patch)?

Ah yes, I think that would be the best solution. Thanks!

[jonpa]

In D71560#1787533, @uweigand wrote:

It seems that the "backchain" attribute does not have to be checked this way, since it is simply present or non-present. Would this be preferrable perhaps also for "packed-stack" (instead of this patch)?

Ah yes, I think that would be the best solution. Thanks!

OK - closing this, then.

llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp

SystemZFrameLowering::SystemZFrameLowering()
   // Create a mapping from register number to save slot offset.
   // These offsets are relative to the start of the register save area.
   RegSpillOffsets.grow(SystemZ::NUM_TARGET_REGS);
   for (unsigned I = 0, E = array_lengthof(SpillOffsetTable); I != E; ++I)
     RegSpillOffsets[SpillOffsetTable[I].Reg] = SpillOffsetTable[I].Offset;
 }
 
 static bool usePackedStack(MachineFunction &MF) {
-  bool HasPackedStackAttr = MF.getFunction().hasFnAttribute("packed-stack");
+  bool PackedStack =
+    MF.getFunction().getFnAttribute("packed-stack").getValueAsString() == "true";
   bool IsVarArg = MF.getFunction().isVarArg();
   bool CallConv = MF.getFunction().getCallingConv() != CallingConv::GHC;
   bool BackChain = MF.getFunction().hasFnAttribute("backchain");
   bool FramAddressTaken = MF.getFrameInfo().isFrameAddressTaken();
-  return HasPackedStackAttr && !IsVarArg && CallConv && !BackChain &&
+  return PackedStack && !IsVarArg && CallConv && !BackChain &&
          !FramAddressTaken;
 }
 
 bool SystemZFrameLowering::
 assignCalleeSavedSpillSlots(MachineFunction &MF,
                             const TargetRegisterInfo *TRI,
                             std::vector<CalleeSavedInfo> &CSI) const {
   SystemZMachineFunctionInfo *ZFI = MF.getInfo<SystemZMachineFunctionInfo>();

llvm/test/CodeGen/SystemZ/frame-22.ll

 ; CHECK-NEXT: lmg     %r6, %r15, 184(%r15)
 ; CHECK-NEXT: br      %r14
   call void asm sideeffect "", "~{f8}"() nounwind
   %C = call i64 @f3 (i64 1, i64 2, i64 3, i64 4, i64 5, i64 6,
                      double 1.0, double 2.0, double 3.0, double 4.0, double 5.0)
   ret i64 %C
 }
 
+; Test that a packed-stack function attribute of "false" gets the default layout.
+define void @f5() #1 {
+; CHECK-LABEL: f5:
+; CHECK: stmg %r12, %r15, 96(%r15)
+; CHECK-NEXT: .cfi_offset %r12, -64
+; CHECK-NEXT: .cfi_offset %r15, -40
+; CHECK-NEXT: aghi %r15, -8
+; CHECK-NEXT: .cfi_def_cfa_offset 168
+; CHECK-NEXT: std %f8, 0(%r15)          # 8-byte Folded Spill
+; CHECK-NEXT: .cfi_offset %f8, -168
+; CHECK-NEXT: #APP
+; CHECK-NEXT: #NO_APP
+; CHECK-NEXT: ld %f8, 0(%r15)          # 8-byte Folded Reload
+; CHECK-NEXT: lmg %r12, %r15, 104(%r15)
+; CHECK-NEXT: br %r14
+  call void asm sideeffect "", "~{f8},~{r12}"() nounwind
+  ret void
+}
+
+
 attributes #0 = { "packed-stack"="true" }
+attributes #1 = { "packed-stack"="false" }