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Fix PR2369 by making scalarrepl more careful about promoting

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structures.  Its default threshold is to promote things that are
smaller than 128 bytes, which is sane.  However, it is not sane
to do this for things that turn into 128 *registers*.  Add a cap
on the number of registers introduced, defaulting to 128/4=32.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52611 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-06-22 17:46:21 +00:00
parent 69bfb15ecd
commit 963a97f1a3
2 changed files with 32 additions and 5 deletions
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17
lib/Transforms/Scalar/ScalarReplAggregates.cpp
View File

@ -178,6 +178,14 @@ bool SROA::performPromotion(Function &F) {
return Changed;
}
/// getNumSAElements - Return the number of elements in the specific struct or
/// array.
static uint64_t getNumSAElements(const Type *T) {
if (const StructType *ST = dyn_cast<StructType>(T))
return ST->getNumElements();
return cast<ArrayType>(T)->getNumElements();
}
// performScalarRepl - This algorithm is a simple worklist driven algorithm,
// which runs on all of the malloc/alloca instructions in the function, removing
// them if they are only used by getelementptr instructions.
@ -224,7 +232,10 @@ bool SROA::performScalarRepl(Function &F) {
(isa<StructType>(AI->getAllocatedType()) ||
isa<ArrayType>(AI->getAllocatedType())) &&
AI->getAllocatedType()->isSized() &&
TD.getABITypeSize(AI->getAllocatedType()) < SRThreshold) {
// Do not promote any struct whose size is larger than "128" bytes.
TD.getABITypeSize(AI->getAllocatedType()) < SRThreshold &&
// Do not promote any struct into more than "32" separate vars.
getNumSAElements(AI->getAllocatedType()) < SRThreshold/4) {
// Check that all of the users of the allocation are capable of being
// transformed.
switch (isSafeAllocaToScalarRepl(AI)) {
@ -672,9 +683,7 @@ void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
// If this is a memcpy/memmove, emit a GEP of the other element address.
Value *OtherElt = 0;
if (OtherPtr) {
Value *Idx[2];
Idx[0] = Zero;
Idx[1] = ConstantInt::get(Type::Int32Ty, i);
Value *Idx[2] = { Zero, ConstantInt::get(Type::Int32Ty, i) };
OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2,
OtherPtr->getNameStr()+"."+utostr(i),
MI);

18
test/Transforms/ScalarRepl/2008-06-22-LargeArray.ll Normal file
View File

@ -0,0 +1,18 @@
; RUN: llvm-as < %s | opt -scalarrepl | llvm-dis | grep {call.*mem}
; PR2369
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin8"
define void @memtest1(i8* %dst, i8* %src) nounwind {
entry:
%temp = alloca [100 x i8] ; <[100 x i8]*> [#uses=2]
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
%temp1 = bitcast [100 x i8]* %temp to i8* ; <i8*> [#uses=1]
call void @llvm.memcpy.i32( i8* %temp1, i8* %src, i32 100, i32 1 )
%temp3 = bitcast [100 x i8]* %temp to i8* ; <i8*> [#uses=1]
call void @llvm.memcpy.i32( i8* %dst, i8* %temp3, i32 100, i32 1 )
ret void
}
declare void @llvm.memcpy.i32(i8*, i8*, i32, i32) nounwind