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[BUG][INDVAR] Fix for PR21014: wrong SCEV operands commuting for non-commutative instructions 

My commit rL216160 introduced a bug PR21014: IndVars widens code 'for (i = ; i < ...; i++) arr[ CONST - i]' into 'for (i = ; i < ...; i++) arr[ i - CONST]'
thus inverting index expression. This patch fixes it. 
Thanks to Jörg Sonnenberger for pointing.

Differential Revision: http://reviews.llvm.org/D5576

llvm-svn: 218867
This commit is contained in:
Zinovy Nis 2014-10-02 13:01:15 +00:00
parent 09c8f6f6a4
commit ccc3e3733b
2 changed files with 18 additions and 5 deletions
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15
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -865,7 +865,8 @@ const SCEVAddRecExpr* WidenIV::GetExtendedOperandRecurrence(NarrowIVDefUse DU) {
// One operand (NarrowDef) has already been extended to WideDef. Now determine
// if extending the other will lead to a recurrence.
unsigned ExtendOperIdx = DU.NarrowUse->getOperand(0) == DU.NarrowDef ? 1 : 0;
const unsigned ExtendOperIdx =
DU.NarrowUse->getOperand(0) == DU.NarrowDef ? 1 : 0;
assert(DU.NarrowUse->getOperand(1-ExtendOperIdx) == DU.NarrowDef && "bad DU");
const SCEV *ExtendOperExpr = nullptr;
@ -885,8 +886,16 @@ const SCEVAddRecExpr* WidenIV::GetExtendedOperandRecurrence(NarrowIVDefUse DU) {
// behavior depends on. Non-control-equivalent instructions can be mapped to
// the same SCEV expression, and it would be incorrect to transfer NSW/NUW
// semantics to those operations.
const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(
GetSCEVByOpCode(SE->getSCEV(DU.WideDef), ExtendOperExpr, OpCode));
const SCEV *lhs = SE->getSCEV(DU.WideDef);
const SCEV *rhs = ExtendOperExpr;
// Let's swap operands to the initial order for the case of non-commutative
// operations, like SUB. See PR21014.
if (ExtendOperIdx == 0)
std::swap(lhs, rhs);
const SCEVAddRecExpr *AddRec =
dyn_cast<SCEVAddRecExpr>(GetSCEVByOpCode(lhs, rhs, OpCode));
if (!AddRec || AddRec->getLoop() != L)
return nullptr;
return AddRec;

8
llvm/test/Transforms/IndVarSimplify/2011-09-10-widen-nsw.ll
View File

@ -19,7 +19,8 @@ for.body153: ; preds = %for.body153, %for.b
; CHECK: add nsw i64 %indvars.iv, 1
; CHECK: sub nsw i64 %indvars.iv, 2
; CHECK: mul nsw i64 %indvars.iv, 4
; CHECK: sub nsw i64 4, %indvars.iv
; CHECK: mul nsw i64 %indvars.iv, 8
for.body170: ; preds = %for.body170, %for.body153
%i2.19 = phi i32 [ %add249, %for.body170 ], [ 0, %for.body153 ]
@ -29,7 +30,10 @@ for.body170: ; preds = %for.body170, %for.b
%sub = sub nsw i32 %i2.19, 2
%sub.idxprom = sext i32 %sub to i64
%mul = mul nsw i32 %i2.19, 4
%sub.neg = sub nsw i32 4, %i2.19
%sub.neg.idxprom = sext i32 %sub.neg to i64
%mul = mul nsw i32 %i2.19, 8
%mul.idxprom = sext i32 %mul to i64
%add249 = add nsw i32 %i2.19, %shl132