| ; RUN: opt < %s -passes=instcombine -S | grep "align 32" | count 2 | |
| ; 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 64 | |
| call void @llvm.memcpy.p0.p0.i32(ptr align 32 @dst, ptr align 32 %src, i32 1024, i1 false) | |
| call void @frob(ptr %src) nounwind | |
| ret void | |
| } | |
| declare void @frob(ptr) | |
| declare void @llvm.memcpy.p0.p0.i32(ptr nocapture, ptr nocapture, i32, i1) nounwind |