llvm-6502/test/Transforms/MemCpyOpt/memcpy-to-memset.ll
Benjamin Kramer a112087e42 MemCpyOpt: Turn memcpys from a constant into a memset if possible.
This allows us to compile "int cst[] = {-1, -1, -1};" into
  movl  $-1, 16(%rsp)
  movq  $-1, 8(%rsp)
instead of
  movl  _cst+8(%rip), %eax
  movl  %eax, 16(%rsp)
  movq  _cst(%rip), %rax
  movq  %rax, 8(%rsp)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122548 91177308-0d34-0410-b5e6-96231b3b80d8
2010-12-24 21:17:12 +00:00

20 lines
696 B
LLVM

; RUN: opt -memcpyopt -S < %s | FileCheck %s
@cst = internal constant [3 x i32] [i32 -1, i32 -1, i32 -1], align 4
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
declare void @foo(i32*) nounwind
define void @test1() nounwind {
%arr = alloca [3 x i32], align 4
%arr_i8 = bitcast [3 x i32]* %arr to i8*
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %arr_i8, i8* bitcast ([3 x i32]* @cst to i8*), i64 12, i32 4, i1 false)
%arraydecay = getelementptr inbounds [3 x i32]* %arr, i64 0, i64 0
call void @foo(i32* %arraydecay) nounwind
ret void
; CHECK: @test1
; CHECK: call void @llvm.memset
; CHECK-NOT: call void @llvm.memcpy
; CHECK: ret void
}