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indvars: Added getInsertPointForUses to find a valid place to truncate the IV.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135568 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick 2011-07-20 05:32:06 +00:00
parent 13bcf2e68a
commit 86c98145b2
2 changed files with 71 additions and 15 deletions
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47
lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -216,6 +216,36 @@ bool IndVarSimplify::isValidRewrite(Value *FromVal, Value *ToVal) {
return true;
}
/// Determine the insertion point for this user. By default, insert immediately
/// before the user. SCEVExpander or LICM will hoist loop invariants out of the
/// loop. For PHI nodes, there may be multiple uses, so compute the nearest
/// common dominator for the incoming blocks.
static Instruction *getInsertPointForUses(Instruction *User, Value *Def,
DominatorTree *DT) {
PHINode *PHI = dyn_cast<PHINode>(User);
if (!PHI)
return User;
Instruction *InsertPt = 0;
for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
if (PHI->getIncomingValue(i) != Def)
continue;
BasicBlock *InsertBB = PHI->getIncomingBlock(i);
if (!InsertPt) {
InsertPt = InsertBB->getTerminator();
continue;
}
InsertBB = DT->findNearestCommonDominator(InsertPt->getParent(), InsertBB);
InsertPt = InsertBB->getTerminator();
}
assert(InsertPt && "Missing phi operand");
assert(!isa<Instruction>(Def) ||
DT->dominates(cast<Instruction>(Def), InsertPt) &&
"def does not dominate all uses");
return InsertPt;
}
//===----------------------------------------------------------------------===//
// RewriteNonIntegerIVs and helpers. Prefer integer IVs.
//===----------------------------------------------------------------------===//
@ -697,18 +727,7 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, SCEVExpander &Rewriter) {
// hoist loop invariants out of the loop. For PHI nodes, there may be
// multiple uses, so compute the nearest common dominator for the
// incoming blocks.
Instruction *InsertPt = User;
if (PHINode *PHI = dyn_cast<PHINode>(InsertPt))
for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
if (PHI->getIncomingValue(i) == Op) {
if (InsertPt == User)
InsertPt = PHI->getIncomingBlock(i)->getTerminator();
else
InsertPt =
DT->findNearestCommonDominator(InsertPt->getParent(),
PHI->getIncomingBlock(i))
->getTerminator();
}
Instruction *InsertPt = getInsertPointForUses(User, Op, DT);
// Now expand it into actual Instructions and patch it into place.
Value *NewVal = Rewriter.expandCodeFor(AR, UseTy, InsertPt);
@ -1023,9 +1042,7 @@ Instruction *WidenIV::WidenIVUse(NarrowIVDefUse DU) {
// This user does not evaluate to a recurence after widening, so don't
// follow it. Instead insert a Trunc to kill off the original use,
// eventually isolating the original narrow IV so it can be removed.
Use *U = std::find(DU.NarrowUse->op_begin(), DU.NarrowUse->op_end(),
DU.NarrowDef);
IRBuilder<> Builder(*U);
IRBuilder<> Builder(getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT));
Value *Trunc = Builder.CreateTrunc(DU.WideDef, DU.NarrowDef->getType());
DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, Trunc);
return 0;

39
test/Transforms/IndVarSimplify/no-iv-rewrite.ll
View File

@ -350,3 +350,42 @@ latch: ; preds = %for.inc50.i
exit:
ret void
}
; Test a widened IV that is used by a phi on different paths within the loop.
;
; CHECK: for.body:
; CHECK: phi i64
; CHECK: trunc i64
; CHECK: if.then:
; CHECK: for.inc:
; CHECK: phi i32
; CHECK: for.end:
define void @phiUsesTrunc() nounwind {
entry:
br i1 undef, label %for.body, label %for.end
for.body:
%iv = phi i32 [ %inc, %for.inc ], [ 1, %entry ]
br i1 undef, label %if.then, label %if.else
if.then:
br i1 undef, label %if.then33, label %for.inc
if.then33:
br label %for.inc
if.else:
br i1 undef, label %if.then97, label %for.inc
if.then97:
%idxprom100 = sext i32 %iv to i64
br label %for.inc
for.inc:
%kmin.1 = phi i32 [ %iv, %if.then33 ], [ 0, %if.then ], [ %iv, %if.then97 ], [ 0, %if.else ]
%inc = add nsw i32 %iv, 1
br i1 undef, label %for.body, label %for.end
for.end:
ret void
}