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When a value is used multiple times within a single PHI, instructions

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inserted to replace that value must dominate all of of the basic
blocks associated with the uses of the value in the PHI, not just
one of them.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74376 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-06-27 05:16:57 +00:00
parent 553e571b43
commit de53dc03f5
2 changed files with 48 additions and 3 deletions
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18
lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -70,6 +70,7 @@ namespace {
IVUsers *IU; IVUsers *IU;
LoopInfo *LI; LoopInfo *LI;
ScalarEvolution *SE; ScalarEvolution *SE;
DominatorTree *DT;
bool Changed; bool Changed;
public: public:
@ -329,6 +330,7 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
IU = &getAnalysis<IVUsers>(); IU = &getAnalysis<IVUsers>();
LI = &getAnalysis<LoopInfo>(); LI = &getAnalysis<LoopInfo>();
SE = &getAnalysis<ScalarEvolution>(); SE = &getAnalysis<ScalarEvolution>();
DT = &getAnalysis<DominatorTree>();
Changed = false; Changed = false;
// If there are any floating-point recurrences, attempt to // If there are any floating-point recurrences, attempt to
@ -479,12 +481,22 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType,
if (!AR->isLoopInvariant(L) && !Stride->isLoopInvariant(L)) if (!AR->isLoopInvariant(L) && !Stride->isLoopInvariant(L))
continue; continue;
// Determine the insertion point for this user. By default, insert
// immediately before the user. The SCEVExpander class will automatically
// 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; Instruction *InsertPt = User;
if (PHINode *PHI = dyn_cast<PHINode>(InsertPt)) if (PHINode *PHI = dyn_cast<PHINode>(InsertPt))
for (unsigned i = 0; ; ++i) for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
if (PHI->getIncomingValue(i) == Op) { if (PHI->getIncomingValue(i) == Op) {
InsertPt = PHI->getIncomingBlock(i)->getTerminator(); if (InsertPt == User)
break; InsertPt = PHI->getIncomingBlock(i)->getTerminator();
else
InsertPt =
DT->findNearestCommonDominator(InsertPt->getParent(),
PHI->getIncomingBlock(i))
->getTerminator();
} }
// Now expand it into actual Instructions and patch it into place. // Now expand it into actual Instructions and patch it into place.

33
test/Transforms/IndVarSimplify/phi-uses-value-multiple-times.ll Normal file
View File

@ -0,0 +1,33 @@
; RUN: llvm-as < %s | opt -indvars
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
@ue = external global i64
define i32 @foo() nounwind {
entry:
br label %bb38.i
bb14.i27:
%t0 = load i64* @ue, align 8
%t1 = sub i64 %t0, %i.0.i35
%t2 = add i64 %t1, 1
br i1 undef, label %bb15.i28, label %bb19.i31
bb15.i28:
br label %bb19.i31
bb19.i31:
%y.0.i = phi i64 [ %t2, %bb15.i28 ], [ %t2, %bb14.i27 ]
br label %bb35.i
bb35.i:
br i1 undef, label %bb37.i, label %bb14.i27
bb37.i:
%t3 = add i64 %i.0.i35, 1
br label %bb38.i
bb38.i:
%i.0.i35 = phi i64 [ 1, %entry ], [ %t3, %bb37.i ]
br label %bb35.i
}