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| author | Chris Lattner <sabre@nondot.org> | 2010-04-26 18:46:46 +0000 |
|---|---|---|
| committer | Chris Lattner <sabre@nondot.org> | 2010-04-26 18:46:46 +0000 |
| commit | f740a8ceebdc5eb626b7d8c075d7c998cc29cc9e (patch) | |
| tree | 46027fd73de4ab1d178c75529a547df9a50a471a | |
| parent | c72d8a7dad755dd33148f84660afdb223797e5a0 (diff) | |
| download | bcm5719-llvm-f740a8ceebdc5eb626b7d8c075d7c998cc29cc9e.tar.gz bcm5719-llvm-f740a8ceebdc5eb626b7d8c075d7c998cc29cc9e.zip | |
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.
llvm-svn: 102365
| -rw-r--r-- | llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp | 10 | ||||
| -rw-r--r-- | llvm/test/CodeGen/X86/alignment.ll | 18 | ||||
| -rw-r--r-- | llvm/test/CodeGen/X86/unaligned-load.ll | 1 |
3 files changed, 28 insertions, 1 deletions
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp index 4660e1b2ccd..6fc883359be 100644 --- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp +++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp @@ -228,7 +228,15 @@ void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) { 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()) { diff --git a/llvm/test/CodeGen/X86/alignment.ll b/llvm/test/CodeGen/X86/alignment.ll new file mode 100644 index 00000000000..06a4f3f8e88 --- /dev/null +++ b/llvm/test/CodeGen/X86/alignment.ll @@ -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. +@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 +@GlobalB = common global { [384 x i8] } zeroinitializer, align 8 + +; CHECK: .comm GlobalB,384,8
\ No newline at end of file diff --git a/llvm/test/CodeGen/X86/unaligned-load.ll b/llvm/test/CodeGen/X86/unaligned-load.ll index e210531068e..b26097f31b4 100644 --- a/llvm/test/CodeGen/X86/unaligned-load.ll +++ b/llvm/test/CodeGen/X86/unaligned-load.ll @@ -28,6 +28,7 @@ return: 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" |
