[llvm-commits] [llvm] r102365 - in /llvm/trunk: lib/CodeGen/AsmPrinter/AsmPrinter.cpp test/CodeGen/X86/alignment.ll test/CodeGen/X86/unaligned-load.ll

[Chris Lattner]

Author: lattner
Date: Mon Apr 26 13:46:46 2010
New Revision: 102365

URL: http://llvm.org/viewvc/llvm-project?rev=102365&view=rev
Log:
fix PR6921 a different way.  Intead of increasing the
alignment of globals with a specified alignment, we fix
common variables to obey their alignment.  Add a comment
explaining why this behavior is important.

Added:
    llvm/trunk/test/CodeGen/X86/alignment.ll
Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
    llvm/trunk/test/CodeGen/X86/unaligned-load.ll

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp?rev=102365&r1=102364&r2=102365&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp Mon Apr 26 13:46:46 2010
@@ -228,7 +228,15 @@
 
   const TargetData *TD = TM.getTargetData();
   unsigned Size = TD->getTypeAllocSize(GV->getType()->getElementType());
-  unsigned AlignLog = TD->getPreferredAlignmentLog(GV);
+  
+  // If the alignment is specified, we *must* obey it.  Overaligning a global
+  // with a specified alignment is a prompt way to break globals emitted to
+  // sections and expected to be contiguous (e.g. ObjC metadata).
+  unsigned AlignLog;
+  if (unsigned GVAlign = GV->getAlignment())
+    AlignLog = Log2_32(GVAlign);
+  else
+    AlignLog = TD->getPreferredAlignmentLog(GV);
   
   // Handle common and BSS local symbols (.lcomm).
   if (GVKind.isCommon() || GVKind.isBSSLocal()) {

Added: llvm/trunk/test/CodeGen/X86/alignment.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/alignment.ll?rev=102365&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/alignment.ll (added)
+++ llvm/trunk/test/CodeGen/X86/alignment.ll Mon Apr 26 13:46:46 2010
@@ -0,0 +1,18 @@
+; RUN: llc %s -o - -mtriple=x86_64-linux-gnu | FileCheck %s
+
+; This cannot get rounded up to the preferred alignment (16) if they have an
+; explicit alignment specified.
+ at GlobalA = global { [384 x i8] } zeroinitializer, align 8 
+
+; CHECK:	.bss
+; CHECK:	.globl	GlobalA
+; CHECK:	.align	8
+; CHECK: GlobalA:
+; CHECK:	.zero	384
+
+; Common variables should not get rounded up to the preferred alignment (16) if
+; they have an explicit alignment specified.
+; PR6921
+ at GlobalB = common global { [384 x i8] } zeroinitializer, align 8
+
+; CHECK: 	.comm	GlobalB,384,8
\ No newline at end of file

Modified: llvm/trunk/test/CodeGen/X86/unaligned-load.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/unaligned-load.ll?rev=102365&r1=102364&r2=102365&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/unaligned-load.ll (original)
+++ llvm/trunk/test/CodeGen/X86/unaligned-load.ll Mon Apr 26 13:46:46 2010
@@ -28,6 +28,7 @@
 
 declare void @llvm.memcpy.i64(i8* nocapture, i8* nocapture, i64, i32) nounwind
 
+; CORE2: .section
 ; CORE2: .align  3
 ; CORE2-NEXT: _.str1:
 ; CORE2-NEXT: .asciz "DHRYSTONE PROGRAM, SOME STRING"