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Create a getelementptr instead of sub expr for ValueOffsetPair if the

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value is a pointer.

This patch is to fix PR30213. When expanding an expr based on ValueOffsetPair,
if the value is of pointer type, we can only create a getelementptr instead
of sub expr.

Differential Revision: https://reviews.llvm.org/D24088

llvm-svn: 281439
This commit is contained in:
Wei Mi 2016-09-14 04:39:50 +00:00
parent 672d508b7d
commit c1cf1864f4
2 changed files with 58 additions and 3 deletions
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25
lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -1703,9 +1703,28 @@ Value *SCEVExpander::expand(const SCEV *S) {
if (!V)
V = visit(S);
else if (VO.second)
V = Builder.CreateSub(V, VO.second);
else if (VO.second) {
if (PointerType *Vty = dyn_cast<PointerType>(V->getType())) {
Type *Ety = Vty->getPointerElementType();
int64_t Offset = VO.second->getSExtValue();
int64_t ESize = SE.getTypeSizeInBits(Ety);
if ((Offset * 8) % ESize == 0) {
ConstantInt *Idx =
ConstantInt::getSigned(VO.second->getType(), -(Offset * 8) / ESize);
V = Builder.CreateGEP(Ety, V, Idx, "scevgep");
} else {
ConstantInt *Idx =
ConstantInt::getSigned(VO.second->getType(), -Offset);
unsigned AS = Vty->getAddressSpace();
V = Builder.CreateBitCast(V, Type::getInt8PtrTy(SE.getContext(), AS));
V = Builder.CreateGEP(Type::getInt8Ty(SE.getContext()), V, Idx,
"uglygep");
V = Builder.CreateBitCast(V, Vty);
}
} else {
V = Builder.CreateSub(V, VO.second);
}
}
// Remember the expanded value for this SCEV at this location.
//
// This is independent of PostIncLoops. The mapped value simply materializes

36
test/Analysis/ScalarEvolution/scev-expander-reuse-gep.ll Normal file
View File

@ -0,0 +1,36 @@
; PR30213. Check scev expand will generate correct code if the value
; in ValueOffsetPair is of pointer type.
; RUN: opt -mtriple=i386-apple-macosx10.12.0 < %s -loop-reduce -S | FileCheck %s
; CHECK: %ptr4.ptr1 = select i1 %cmp.i, i8* %ptr4, i8* %ptr1
; CHECK-NEXT: %scevgep = getelementptr i8, i8* %ptr4.ptr1, i32 1
; CHECK-NEXT: br label %while.cond.i
target datalayout = "e-m:o-p:32:32-f64:32:64-f80:128-n8:16:32-S128"
target triple = "i386-apple-macosx10.12.0"
; Function Attrs: nounwind optsize ssp
define void @Foo() {
entry:
switch i2 undef, label %sw.epilog102 [
i2 -2, label %sw.bb28
]
sw.bb28: ; preds = %entry
%0 = load i8*, i8** undef, align 2
%ptr1 = getelementptr inbounds i8, i8* undef, i32 -1
%ptr4 = getelementptr inbounds i8, i8* %0, i32 -1
%cmp.i = icmp ult i8* undef, %0
%ptr4.ptr1 = select i1 %cmp.i, i8* %ptr4, i8* %ptr1
br label %while.cond.i
while.cond.i: ; preds = %while.cond.i, %sw.bb28
%currPtr.1.i = phi i8* [ %incdec.ptr.i, %while.cond.i ], [ %ptr4.ptr1, %sw.bb28 ]
%incdec.ptr.i = getelementptr inbounds i8, i8* %currPtr.1.i, i32 1
%1 = load i8, i8* %incdec.ptr.i, align 1
br label %while.cond.i
sw.epilog102: ; preds = %entry
unreachable
}