forked from OSchip/llvm-project
30 lines
1.2 KiB
LLVM
30 lines
1.2 KiB
LLVM
; RUN: opt < %s -instcombine -S | grep {align 32} | count 1
|
|
|
|
; It's tempting to have an instcombine in which the src pointer of a
|
|
; memcpy is aligned up to the alignment of the destination, however
|
|
; there are pitfalls. If the src is an alloca, aligning it beyond what
|
|
; the target's stack pointer is aligned at will require dynamic
|
|
; stack realignment, which can require functions that don't otherwise
|
|
; need a frame pointer to need one.
|
|
;
|
|
; Abstaining from this transform is not the only way to approach this
|
|
; issue. Some late phase could be smart enough to reduce alloca
|
|
; alignments when they are greater than they need to be. Or, codegen
|
|
; could do dynamic alignment for just the one alloca, and leave the
|
|
; main stack pointer at its standard alignment.
|
|
|
|
@dst = global [1024 x i8] zeroinitializer, align 32
|
|
|
|
define void @foo() nounwind {
|
|
entry:
|
|
%src = alloca [1024 x i8], align 1
|
|
%src1 = getelementptr [1024 x i8]* %src, i32 0, i32 0
|
|
call void @llvm.memcpy.i32(i8* getelementptr ([1024 x i8]* @dst, i32 0, i32 0), i8* %src1, i32 1024, i32 1)
|
|
call void @frob(i8* %src1) nounwind
|
|
ret void
|
|
}
|
|
|
|
declare void @llvm.memcpy.i32(i8* nocapture, i8* nocapture, i32, i32) nounwind
|
|
|
|
declare void @frob(i8*)
|