[PATCH] D21611: Fix small structures calling convention issue for some big endian architectures

[Strahinja Petrovic via cfe-commits]

spetrovic created this revision.
spetrovic added reviewers: rjmccall, john.brawn, dsanders, petarj.
spetrovic added subscribers: cfe-commits, rankov, ivanbaev.
Herald added a reviewer: vkalintiris.
Herald added a subscriber: aemerson.

This patch fixes problem with passing structures and unions smaller than register as argument in variadic functions
on big endian architectures. 
For example passing 3 chars in a structure as argument of variadic function LLVM is passing those chars 
left-adjusted in register and trying to read them like they are right-adjusted, and that makes the problem.
I have changed reading of those arguments. Now LLVM reads them properly (left-adjusted). I detected
this problem on ARM32 big endian, MIPS32 big endian and MIPS64 big endian.

http://reviews.llvm.org/D21611

Files:
  lib/CodeGen/TargetInfo.cpp
  test/CodeGen/struct-union-BE.c

Index: test/CodeGen/struct-union-BE.c
===================================================================
--- test/CodeGen/struct-union-BE.c
+++ test/CodeGen/struct-union-BE.c
@@ -0,0 +1,48 @@
+// RUN: %clang -O2 -target mips-linux-gnu  -EB -S -emit-llvm %s -o - | FileCheck %s -check-prefix=MIPS
+// RUN: %clang -O2 -target mips64-linux-gnu  -EB -S -emit-llvm %s -o - | FileCheck %s -check-prefix=MIPS64
+// RUN: %clang -O2 -target armeb-linux-gnueabihf -march=armv7a  -EB -S -emit-llvm %s -o - | FileCheck %s -check-prefix=ARM
+
+#include <stdarg.h>
+#include <stdlib.h>
+
+struct tiny {
+  char c;
+};
+
+union data {
+  char c;
+};
+
+void fstr(int n, ...) {
+  struct tiny x;
+  va_list ap;
+  va_start (ap,n);
+  x = va_arg (ap, struct tiny);
+  if (x.c !=  10)
+    abort();
+  va_end (ap);
+// MIPS-NOT: %{{[0-9]+}} = getelementptr inbounds i8, i8* %argp.cur, i32 3
+// MIPS64-NOT: %{{[0-9]+}} = getelementptr inbounds i8, i8* %argp.cur, i64 7
+// ARM-NOT: %{{[0-9]+}} = getelementptr inbounds i8, i8* %argp.cur, i32 3
+}
+
+void funi(int n, ...) {
+  union data x;
+  va_list ap;
+  va_start (ap,n);
+  x = va_arg (ap, union data);
+  if (x.c !=  10)
+    abort();
+  va_end (ap);
+// MIPS-NOT: %{{[0-9]+}} = getelementptr inbounds i8, i8* %argp.cur, i32 3
+// MIPS64-NOT: %{{[0-9]+}} = getelementptr inbounds i8, i8* %argp.cur, i64 7
+// ARM-NOT: %{{[0-9]+}} = getelementptr inbounds i8, i8* %argp.cur, i32 3
+}
+
+void foo() {
+  struct tiny x[3];
+  union data y;
+  x[0].c = 10;
+  fstr(1, x[0]);
+  funi(1, y);
+}
Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp
+++ lib/CodeGen/TargetInfo.cpp
@@ -272,7 +272,8 @@
 
   // If the argument is smaller than a slot, and this is a big-endian
   // target, the argument will be right-adjusted in its slot.
-  if (DirectSize < SlotSize && CGF.CGM.getDataLayout().isBigEndian()) {
+  if (DirectSize < SlotSize && CGF.CGM.getDataLayout().isBigEndian() &&
+      !DirectTy->isStructTy()) {
     Addr = CGF.Builder.CreateConstInBoundsByteGEP(Addr, SlotSize - DirectSize);
   }
 


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