[PATCH] [mips] Fix va_arg() for pointer types on big-endian N32.

[Daniel Sanders]

Hi atanasyan, vmedic,

The Mips ABI's treat pointers in the same way as integers. They are
sign-extended to 32-bit for O32, and 64-bit for N32/N64. This doesn't matter
for O32 and N64 where pointers are already the correct width but it does matter
for big-endian N32, where pointers are 32-bit and need promoting.

The caller side is already passing pointers correctly. This patch corrects the
callee.

http://reviews.llvm.org/D6812

Files:
  lib/CodeGen/CGExprScalar.cpp
  lib/CodeGen/TargetInfo.cpp
  test/CodeGen/mips-varargs.c

Index: lib/CodeGen/CGExprScalar.cpp
===================================================================
--- lib/CodeGen/CGExprScalar.cpp
+++ lib/CodeGen/CGExprScalar.cpp
@@ -3232,8 +3232,12 @@
   llvm::Value *Val = Builder.CreateLoad(ArgPtr);
 
   // If EmitVAArg promoted the type, we must truncate it.
-  if (ArgTy != Val->getType())
-    Val = Builder.CreateTrunc(Val, ArgTy);
+  if (ArgTy != Val->getType()) {
+    if (ArgTy->isPointerTy() && !Val->getType()->isPointerTy())
+      Val = Builder.CreateIntToPtr(Val, ArgTy);
+    else
+      Val = Builder.CreateTrunc(Val, ArgTy);
+  }
 
   return Val;
 }
Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp
+++ lib/CodeGen/TargetInfo.cpp
@@ -5562,10 +5562,13 @@
   llvm::Type *BP = CGF.Int8PtrTy;
   llvm::Type *BPP = CGF.Int8PtrPtrTy;
 
-  // Integer arguments are promoted 32-bit on O32 and 64-bit on N32/N64.
+  // Integer arguments are promoted to 32-bit on O32 and 64-bit on N32/N64.
+  // Pointers are also promoted in the same way but this only matters for N32.
   unsigned SlotSizeInBits = IsO32 ? 32 : 64;
-  if (Ty->isIntegerType() &&
-      CGF.getContext().getIntWidth(Ty) < SlotSizeInBits) {
+  unsigned PtrWidth = getTarget().getPointerWidth(0);
+  if ((Ty->isIntegerType() &&
+          CGF.getContext().getIntWidth(Ty) < SlotSizeInBits) ||
+      (Ty->isPointerType() && PtrWidth < SlotSizeInBits)) {
     Ty = CGF.getContext().getIntTypeForBitwidth(SlotSizeInBits,
                                                 Ty->isSignedIntegerType());
   }
@@ -5577,7 +5580,6 @@
       std::min(getContext().getTypeAlign(Ty) / 8, StackAlignInBytes);
   llvm::Type *PTy = llvm::PointerType::getUnqual(CGF.ConvertType(Ty));
   llvm::Value *AddrTyped;
-  unsigned PtrWidth = getTarget().getPointerWidth(0);
   llvm::IntegerType *IntTy = (PtrWidth == 32) ? CGF.Int32Ty : CGF.Int64Ty;
 
   if (TypeAlign > MinABIStackAlignInBytes) {
Index: test/CodeGen/mips-varargs.c
===================================================================
--- test/CodeGen/mips-varargs.c
+++ test/CodeGen/mips-varargs.c
@@ -136,6 +136,46 @@
 // ALL:   ret i64 [[ARG1]]
 // ALL: }
 
+char *test_ptr(char *fmt, ...) {
+  va_list va;
+
+  va_start(va, fmt);
+  char *v = va_arg(va, char *);
+  va_end(va);
+
+  return v;
+}
+
+// ALL-LABEL: define i8* @test_ptr(i8*{{.*}} %fmt, ...)
+//
+// O32:   %va = alloca i8*, align [[PTRALIGN:4]]
+// N32:   %va = alloca i8*, align [[PTRALIGN:4]]
+// N64:   %va = alloca i8*, align [[PTRALIGN:8]]
+//
+// ALL:   [[VA1:%.+]] = bitcast i8** %va to i8*
+// ALL:   call void @llvm.va_start(i8* [[VA1]])
+//
+// ALL:   [[AP_CUR:%.+]] = load i8** %va, align [[PTRALIGN]]
+//
+// O32:   [[TMP0:%.+]] = bitcast i8* [[AP_CUR]] to i8**
+// N32:   [[TMP0:%.+]] = bitcast i8* [[AP_CUR]] to i64*
+// N64:   [[TMP0:%.+]] = bitcast i8* [[AP_CUR]] to i8**
+//
+// O32:   [[AP_NEXT:%.+]] = getelementptr i8* [[AP_CUR]], i32 4
+// NEW:   [[AP_NEXT:%.+]] = getelementptr i8* [[AP_CUR]], {{i32|i64}} 8
+//
+// ALL:   store i8* [[AP_NEXT]], i8** %va, align [[PTRALIGN]]
+//
+// O32:   [[ARG1:%.+]] = load i8** [[TMP0]], align 4
+// N32:   [[TMP2:%.+]] = load i64* [[TMP0]], align 8
+// N32:   [[TMP3:%.+]] = trunc i64 [[TMP2]] to i32
+// N32:   [[ARG1:%.+]] = inttoptr i32 [[TMP3]] to i8*
+// N64:   [[ARG1:%.+]] = load i8** [[TMP0]], align 8
+//
+// ALL:   call void @llvm.va_end(i8* [[VA1]])
+// ALL:   ret i8* [[ARG1]]
+// ALL: }
+
 int test_v4i32(char *fmt, ...) {
   va_list va;

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