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Make SROA more aggressive with allocas containing padding.

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SROA only split up structs and arrays one level at a time, so padding can
only cause trouble if it is located in between the struct or array elements.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123380 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bob Wilson 2011-01-13 17:45:08 +00:00
parent 3bf2279411
commit 694a10e7d8
2 changed files with 59 additions and 39 deletions
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69
lib/Transforms/Scalar/ScalarReplAggregates.cpp
View File

@ -1676,46 +1676,39 @@ void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
}
/// HasPadding - Return true if the specified type has any structure or
/// alignment padding, false otherwise.
/// alignment padding in between the elements that would be split apart
/// by SROA; return false otherwise.
static bool HasPadding(const Type *Ty, const TargetData &TD) {
if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
return HasPadding(ATy->getElementType(), TD);
if (const VectorType *VTy = dyn_cast<VectorType>(Ty))
return HasPadding(VTy->getElementType(), TD);
if (const StructType *STy = dyn_cast<StructType>(Ty)) {
const StructLayout *SL = TD.getStructLayout(STy);
unsigned PrevFieldBitOffset = 0;
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
// Padding in sub-elements?
if (HasPadding(STy->getElementType(i), TD))
return true;
// Check to see if there is any padding between this element and the
// previous one.
if (i) {
unsigned PrevFieldEnd =
PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
if (PrevFieldEnd < FieldBitOffset)
return true;
}
PrevFieldBitOffset = FieldBitOffset;
}
// Check for tail padding.
if (unsigned EltCount = STy->getNumElements()) {
unsigned PrevFieldEnd = PrevFieldBitOffset +
TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
if (PrevFieldEnd < SL->getSizeInBits())
return true;
}
if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
Ty = ATy->getElementType();
return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
}
return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
// SROA currently handles only Arrays and Structs.
const StructType *STy = cast<StructType>(Ty);
const StructLayout *SL = TD.getStructLayout(STy);
unsigned PrevFieldBitOffset = 0;
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
// Check to see if there is any padding between this element and the
// previous one.
if (i) {
unsigned PrevFieldEnd =
PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
if (PrevFieldEnd < FieldBitOffset)
return true;
}
PrevFieldBitOffset = FieldBitOffset;
}
// Check for tail padding.
if (unsigned EltCount = STy->getNumElements()) {
unsigned PrevFieldEnd = PrevFieldBitOffset +
TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
if (PrevFieldEnd < SL->getSizeInBits())
return true;
}
return false;
}
/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of

29
test/Transforms/ScalarRepl/copy-aggregate.ll
View File

@ -1,9 +1,11 @@
; RUN: opt < %s -scalarrepl -S | not grep alloca
; RUN: opt < %s -scalarrepl -S | FileCheck %s
; PR3290
target datalayout = "E-p:64:64:64-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"
;; Store of integer to whole alloca struct.
define i32 @test1(i64 %V) nounwind {
; CHECK: test1
; CHECK-NOT: alloca
%X = alloca {{i32, i32}}
%Y = bitcast {{i32,i32}}* %X to i64*
store i64 %V, i64* %Y
@ -18,6 +20,8 @@ define i32 @test1(i64 %V) nounwind {
;; Store of integer to whole struct/array alloca.
define float @test2(i128 %V) nounwind {
; CHECK: test2
; CHECK-NOT: alloca
%X = alloca {[4 x float]}
%Y = bitcast {[4 x float]}* %X to i128*
store i128 %V, i128* %Y
@ -32,6 +36,8 @@ define float @test2(i128 %V) nounwind {
;; Load of whole alloca struct as integer
define i64 @test3(i32 %a, i32 %b) nounwind {
; CHECK: test3
; CHECK-NOT: alloca
%X = alloca {{i32, i32}}
%A = getelementptr {{i32,i32}}* %X, i32 0, i32 0, i32 0
@ -46,6 +52,8 @@ define i64 @test3(i32 %a, i32 %b) nounwind {
;; load of integer from whole struct/array alloca.
define i128 @test4(float %a, float %b) nounwind {
; CHECK: test4
; CHECK-NOT: alloca
%X = alloca {[4 x float]}
%A = getelementptr {[4 x float]}* %X, i32 0, i32 0, i32 0
%B = getelementptr {[4 x float]}* %X, i32 0, i32 0, i32 3
@ -56,3 +64,22 @@ define i128 @test4(float %a, float %b) nounwind {
%V = load i128* %Y
ret i128 %V
}
;; If the elements of a struct or array alloca contain padding, SROA can still
;; split up the alloca as long as there is no padding between the elements.
%padded = type { i16, i8 }
%arr = type [4 x %padded]
define void @test5(%arr* %p, %arr* %q) {
entry:
; CHECK: test5
; CHECK-NOT: i128
%var = alloca %arr, align 4
%vari8 = bitcast %arr* %var to i8*
%pi8 = bitcast %arr* %p to i8*
call void @llvm.memcpy.i32(i8* %vari8, i8* %pi8, i32 16, i32 4)
%qi8 = bitcast %arr* %q to i8*
call void @llvm.memcpy.i32(i8* %qi8, i8* %vari8, i32 16, i32 4)
ret void
}
declare void @llvm.memcpy.i32(i8* nocapture, i8* nocapture, i32, i32) nounwind