[llvm-commits] [PATCH] [msan] Change va_start/va_copy shadow memcpy alignment to 8

[Peter Collingbourne]

Hi eugenis,

This fixes va_start/va_copy of a va_list field which happens to not
be laid out at a 16-byte boundary.

http://llvm-reviews.chandlerc.com/D276

Files:
  lib/Transforms/Instrumentation/MemorySanitizer.cpp
  test/Instrumentation/MemorySanitizer/msan_basic.ll

Index: lib/Transforms/Instrumentation/MemorySanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -1774,7 +1774,7 @@
     // Unpoison the whole __va_list_tag.
     // FIXME: magic ABI constants.
     IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
-                     /* size */24, /* alignment */16, false);
+                     /* size */24, /* alignment */8, false);
   }
 
   void visitVACopyInst(VACopyInst &I) {
@@ -1785,7 +1785,7 @@
     // Unpoison the whole __va_list_tag.
     // FIXME: magic ABI constants.
     IRB.CreateMemSet(ShadowPtr, Constant::getNullValue(IRB.getInt8Ty()),
-                     /* size */ 24, /* alignment */ 16, false);
+                     /* size */ 24, /* alignment */ 8, false);
   }
 
   void finalizeInstrumentation() {
Index: test/Instrumentation/MemorySanitizer/msan_basic.ll
===================================================================
--- test/Instrumentation/MemorySanitizer/msan_basic.ll
+++ test/Instrumentation/MemorySanitizer/msan_basic.ll
@@ -534,3 +534,15 @@
 ; CHECK: load <8 x i8*>*
 ; CHECK: store <8 x i64> {{.*}} @__msan_retval_tls
 ; CHECK: ret <8 x i8*>
+
+; Test handling of va_copy.
+
+declare void @llvm.va_copy(i8*, i8*) nounwind
+
+define void @VACopy(i8* %p1, i8* %p2) nounwind uwtable {
+  call void @llvm.va_copy(i8* %p1, i8* %p2) nounwind
+  ret void
+}
+
+; CHECK: @VACopy
+; CHECK: call void @llvm.memset.p0i8.i64({{.*}}, i8 0, i64 24, i32 8, i1 false)
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