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SROA: Only split loads on byte boundaries

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r199771 accidently broke the logic that makes sure that SROA only splits
load on byte boundaries.  If such a split happens, some bits get lost
when reassembling loads of wider types, causing data corruption.

Move the width check up to reject such splits early, avoiding the
corruption.  Fixes PR19250.

Patch by: Björn Steinbrink <bsteinbr@gmail.com>

llvm-svn: 211082
This commit is contained in:
Duncan P. N. Exon Smith 2014-06-17 00:19:35 +00:00
parent fab75e134e
commit dbf049d50f
3 changed files with 69 additions and 5 deletions
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12
lib/Transforms/Scalar/SROA.cpp
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@ -1032,11 +1032,6 @@ static Type *findCommonType(AllocaSlices::const_iterator B,
UserTy = SI->getValueOperand()->getType();
}
if (!UserTy || (Ty && Ty != UserTy))
TyIsCommon = false; // Give up on anything but an iN type.
else
Ty = UserTy;
if (IntegerType *UserITy = dyn_cast_or_null<IntegerType>(UserTy)) {
// If the type is larger than the partition, skip it. We only encounter
// this for split integer operations where we want to use the type of the
@ -1051,6 +1046,13 @@ static Type *findCommonType(AllocaSlices::const_iterator B,
if (!ITy || ITy->getBitWidth() < UserITy->getBitWidth())
ITy = UserITy;
}
// To avoid depending on the order of slices, Ty and TyIsCommon must not
// depend on types skipped above.
if (!UserTy || (Ty && Ty != UserTy))
TyIsCommon = false; // Give up on anything but an iN type.
else
Ty = UserTy;
}
return TyIsCommon ? Ty : ITy;

37
test/Transforms/SROA/slice-order-independence.ll Normal file
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@ -0,0 +1,37 @@
; 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"
declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32, i1) nounwind
; Check that the chosen type for a split is independent from the order of
; slices even in case of types that are skipped because their width is not a
; byte width multiple
define void @skipped_inttype_first({ i16*, i32 }*) {
; CHECK-LABEL: @skipped_inttype_first
; CHECK: alloca i8*
%arg = alloca { i16*, i32 }, align 8
%2 = bitcast { i16*, i32 }* %0 to i8*
%3 = bitcast { i16*, i32 }* %arg to i8*
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %3, i8* %2, i32 16, i32 8, i1 false)
%b = getelementptr inbounds { i16*, i32 }* %arg, i64 0, i32 0
%pb0 = bitcast i16** %b to i63*
%b0 = load i63* %pb0
%pb1 = bitcast i16** %b to i8**
%b1 = load i8** %pb1
ret void
}
define void @skipped_inttype_last({ i16*, i32 }*) {
; CHECK-LABEL: @skipped_inttype_last
; CHECK: alloca i8*
%arg = alloca { i16*, i32 }, align 8
%2 = bitcast { i16*, i32 }* %0 to i8*
%3 = bitcast { i16*, i32 }* %arg to i8*
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %3, i8* %2, i32 16, i32 8, i1 false)
%b = getelementptr inbounds { i16*, i32 }* %arg, i64 0, i32 0
%pb1 = bitcast i16** %b to i8**
%b1 = load i8** %pb1
%pb0 = bitcast i16** %b to i63*
%b0 = load i63* %pb0
ret void
}

25
test/Transforms/SROA/slice-width.ll Normal file
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@ -0,0 +1,25 @@
; 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"
declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, 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
%arg = alloca i32 , align 8
store i32 %0, i32* %arg
br label %load_i32
load_i32:
; CHECK-LABEL: load_i32:
; CHECK-NOT: bitcast {{.*}} to i1
; CHECK-NOT: zext i1
%r0 = load i32* %arg
br label %load_i1
load_i1:
; CHECK-LABEL: load_i1:
; CHECK: bitcast {{.*}} to i1
%p1 = bitcast i32* %arg to i1*
%t1 = load i1* %p1
ret void
}