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8081057fca
There's no point in copying around constants, so, when all else fails, we can still transform memcpy of memset into two independent memsets. To quote the example, we can turn: memset(dst1, c, dst1_size); memcpy(dst2, dst1, dst2_size); into: memset(dst1, c, dst1_size); memset(dst2, c, dst2_size); When dst2_size <= dst1_size. Like r235232 for copy constructors, this can occur in move constructors. Differential Revision: http://reviews.llvm.org/D9682 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237506 91177308-0d34-0410-b5e6-96231b3b80d8
31 lines
1.5 KiB
LLVM
31 lines
1.5 KiB
LLVM
; RUN: opt < %s -S -basicaa -memcpyopt | FileCheck %s
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target datalayout = "e-i64:64-f80:128-n8:16:32:64-S128"
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declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1) unnamed_addr nounwind
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declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
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; all bytes of %dst that are touch by the memset are dereferenceable
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define void @must_remove_memcpy(i8* noalias nocapture dereferenceable(4096) %dst) {
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; CHECK-LABEL: @must_remove_memcpy(
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; CHECK: call void @llvm.memset.p0i8.i64
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; CHECK-NOT: call void @llvm.memcpy.p0i8.p0i8.i64
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%src = alloca [4096 x i8], align 1
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%p = getelementptr inbounds [4096 x i8], [4096 x i8]* %src, i64 0, i64 0
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call void @llvm.memset.p0i8.i64(i8* %p, i8 0, i64 4096, i32 1, i1 false)
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call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %p, i64 4096, i32 1, i1 false) #2
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ret void
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}
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; memset touch more bytes than those guaranteed to be dereferenceable
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; We can't remove the memcpy, but we can turn it into an independent memset.
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define void @must_not_remove_memcpy(i8* noalias nocapture dereferenceable(1024) %dst) {
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; CHECK-LABEL: @must_not_remove_memcpy(
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; CHECK: call void @llvm.memset.p0i8.i64
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; CHECK: call void @llvm.memset.p0i8.i64
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%src = alloca [4096 x i8], align 1
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%p = getelementptr inbounds [4096 x i8], [4096 x i8]* %src, i64 0, i64 0
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call void @llvm.memset.p0i8.i64(i8* %p, i8 0, i64 4096, i32 1, i1 false)
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call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %p, i64 4096, i32 1, i1 false) #2
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ret void
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}
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