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SROA: Handle a case of store size being smaller than allocation size 

In this case, we are creating an x86_fp80 slice for a union from C where
the padding bytes may contain real data. An x86_fp80 alloca is 16 bytes,
and that's just fine. We can't, however, use regular loads and stores to
access the slice, because the store size is only 10 bytes / 80 bits.
Instead, use memcpy and memset.

Fixes PR18726.

Reviewed By: chandlerc

Differential Revision: http://reviews.llvm.org/D5012

llvm-svn: 216248
This commit is contained in:
Reid Kleckner 2014-08-22 00:09:56 +00:00
parent c25146b67b
commit c36f48f08a
2 changed files with 54 additions and 5 deletions
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10
llvm/lib/Transforms/Scalar/SROA.cpp
View File

@ -2422,6 +2422,7 @@ private:
if (!VecTy && !IntTy &&
(BeginOffset > NewAllocaBeginOffset ||
EndOffset < NewAllocaEndOffset ||
SliceSize != DL.getTypeStoreSize(AllocaTy) ||
!AllocaTy->isSingleValueType() ||
!DL.isLegalInteger(DL.getTypeSizeInBits(ScalarTy)) ||
DL.getTypeSizeInBits(ScalarTy)%8 != 0)) {
@ -2544,10 +2545,11 @@ private:
// If this doesn't map cleanly onto the alloca type, and that type isn't
// a single value type, just emit a memcpy.
bool EmitMemCpy
= !VecTy && !IntTy && (BeginOffset > NewAllocaBeginOffset ||
EndOffset < NewAllocaEndOffset ||
!NewAI.getAllocatedType()->isSingleValueType());
bool EmitMemCpy =
!VecTy && !IntTy &&
(BeginOffset > NewAllocaBeginOffset || EndOffset < NewAllocaEndOffset ||
SliceSize != DL.getTypeStoreSize(NewAI.getAllocatedType()) ||
!NewAI.getAllocatedType()->isSingleValueType());
// If we're just going to emit a memcpy, the alloca hasn't changed, and the
// size hasn't been shrunk based on analysis of the viable range, this is

49
llvm/test/Transforms/SROA/slice-width.ll
View File

@ -1,7 +1,8 @@
; RUN: opt < %s -sroa -S | FileCheck %s
target datalayout = "e-p:64:64:64-p1:16:16:16-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-n8:16:32:64"
target datalayout = "e-p:64:64:64-p1:16:16:16-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:64:64-f80:128-v64:64:64-v128:128:128-a0:0:64-n8:16:32:64"
declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32, i1) nounwind
declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) nounwind
define void @no_split_on_non_byte_width(i32) {
; This tests that allocas are not split into slices that are not byte width multiple
@ -23,3 +24,49 @@ load_i1:
%t1 = load i1* %p1
ret void
}
; PR18726: Check that we use memcpy and memset to fill out padding when we have
; a slice with a simple single type whose store size is smaller than the slice
; size.
%union.Foo = type { x86_fp80, i64, i64 }
@foo_copy_source = external constant %union.Foo
@i64_sink = global i64 0
define void @memcpy_fp80_padding() {
%x = alloca %union.Foo
; Copy from a global.
%x_i8 = bitcast %union.Foo* %x to i8*
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %x_i8, i8* bitcast (%union.Foo* @foo_copy_source to i8*), i32 32, i32 16, i1 false)
; Access a slice of the alloca to trigger SROA.
%mid_p = getelementptr %union.Foo* %x, i32 0, i32 1
%elt = load i64* %mid_p
store i64 %elt, i64* @i64_sink
ret void
}
; CHECK-LABEL: define void @memcpy_fp80_padding
; CHECK: alloca x86_fp80
; CHECK: call void @llvm.memcpy.p0i8.p0i8.i32
; CHECK: load i64* getelementptr inbounds (%union.Foo* @foo_copy_source, i64 0, i32 1)
; CHECK: load i64* getelementptr inbounds (%union.Foo* @foo_copy_source, i64 0, i32 2)
define void @memset_fp80_padding() {
%x = alloca %union.Foo
; Set to all ones.
%x_i8 = bitcast %union.Foo* %x to i8*
call void @llvm.memset.p0i8.i32(i8* %x_i8, i8 -1, i32 32, i32 16, i1 false)
; Access a slice of the alloca to trigger SROA.
%mid_p = getelementptr %union.Foo* %x, i32 0, i32 1
%elt = load i64* %mid_p
store i64 %elt, i64* @i64_sink
ret void
}
; CHECK-LABEL: define void @memset_fp80_padding
; CHECK: alloca x86_fp80
; CHECK: call void @llvm.memset.p0i8.i32(i8* %{{.*}}, i8 -1, i32 16, i32 16, i1 false)
; CHECK: store i64 -1, i64* @i64_sink