[PATCH] D141370: AArch64: allocate small fixed args properly in varargs functions.

[Tim Northover via Phabricator via llvm-commits]

t.p.northover created this revision.
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Quite an embarrassing one here, vargargs calls have been broken in some edge-cases for quite a while...

On Darwin, function arguments occupy their real size when passed on the stack (e.g. an i16 only consumes 2 bytes). This means that, even for fixed args in varargs calls we need to keep track of the original type being passed before any DAG/GISel promotions. Existing logic only applied this fix to the non-varargs case leading to mismatch between caller & callee in those situations.

On Linux & Windows these arguments always occupy a 64-bit slot anyway so there's no special handling needed.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D141370

Files:
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp
  llvm/test/CodeGen/AArch64/varargs-fixed-i16.ll


Index: llvm/test/CodeGen/AArch64/varargs-fixed-i16.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/varargs-fixed-i16.ll
@@ -0,0 +1,23 @@
+; RUN: llc -mtriple=arm64-apple-macosx %s -o - | FileCheck %s --check-prefix=CHECK-DARWIN
+; RUN: llc -mtriple=arm64-apple-macosx %s -o - -global-isel | FileCheck %s --check-prefix=CHECK-DARWIN
+; RUN: llc -mtriple=aarch64-linux-gnu %s -o - | FileCheck %s --check-prefix=CHECK-LINWIN
+; RUN: llc -mtriple=aarch64-linux-gnu %s -o - -global-isel | FileCheck %s --check-prefix=CHECK-LINWIN
+; RUN: llc -mtriple=aarch64-windows-msvc %s -o - | FileCheck %s --check-prefix=CHECK-LINWIN
+; RUN: llc -mtriple=aarch64-windows-msvc %s -o - -global-isel | FileCheck %s --check-prefix=CHECK-LINWIN
+
+declare i16 @foo([8 x i64], i16 signext, i16 signext %a, ...)
+
+define void @bar() {
+; CHECK-DARWIN-LABEL: bar:
+; CHECK-LINWIN-LABEL: bar:
+
+; CHECK-DARWIN: mov [[TMP:w[0-9]+]], #2752512
+; CHECK-DARWIN: str [[TMP]], [sp]
+
+; CHECK-LINWIN: mov [[TMP:w[0-9]+]], #42
+; CHECK-LINWIN: str{{h?}} wzr, [sp]
+; CHECK-LINWIN: str{{h?}} [[TMP]], [sp, #8]
+
+  call i16([8 x i64], i16, i16, ...) @foo([8 x i64] poison, i16 signext 0, i16 signext 42)
+  ret void
+}
Index: llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp
===================================================================
--- llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp
+++ llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp
@@ -115,13 +115,12 @@
     bool IsCalleeWin = Subtarget.isCallingConvWin64(State.getCallingConv());
     bool UseVarArgsCCForFixed = IsCalleeWin && State.isVarArg();
 
-    if (!State.isVarArg() && !UseVarArgsCCForFixed && !IsReturn)
-      applyStackPassedSmallTypeDAGHack(OrigVT, ValVT, LocVT);
-
     bool Res;
-    if (Info.IsFixed && !UseVarArgsCCForFixed)
+    if (Info.IsFixed && !UseVarArgsCCForFixed) {
+      if (!IsReturn)
+        applyStackPassedSmallTypeDAGHack(OrigVT, ValVT, LocVT);
       Res = AssignFn(ValNo, ValVT, LocVT, LocInfo, Flags, State);
-    else
+    } else
       Res = AssignFnVarArg(ValNo, ValVT, LocVT, LocInfo, Flags, State);
 
     StackOffset = State.getNextStackOffset();
Index: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -6916,7 +6916,9 @@
       } else {
         UseVarArgCC = !Outs[i].IsFixed;
       }
-    } else {
+    }
+
+    if (!UseVarArgCC) {
       // Get type of the original argument.
       EVT ActualVT =
           TLI.getValueType(DAG.getDataLayout(), CLI.Args[Outs[i].OrigArgIndex].Ty,


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