diff options
| -rw-r--r-- | llvm/lib/Transforms/Scalar/IndVarSimplify.cpp | 29 | ||||
| -rw-r--r-- | llvm/test/Transforms/IndVarSimplify/pr25576.ll | 31 |
2 files changed, 37 insertions, 23 deletions
diff --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp index 4f0270896f1..0a41e7164cd 100644 --- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp +++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp @@ -504,10 +504,9 @@ struct RewritePhi { unsigned Ith; // Ith incoming value. Value *Val; // Exit value after expansion. bool HighCost; // High Cost when expansion. - bool SafePhi; // LCSSASafePhiForRAUW. - RewritePhi(PHINode *P, unsigned I, Value *V, bool H, bool S) - : PN(P), Ith(I), Val(V), HighCost(H), SafePhi(S) {} + RewritePhi(PHINode *P, unsigned I, Value *V, bool H) + : PN(P), Ith(I), Val(V), HighCost(H) {} }; } @@ -560,21 +559,6 @@ void IndVarSimplify::rewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) { unsigned NumPreds = PN->getNumIncomingValues(); - // We would like to be able to RAUW single-incoming value PHI nodes. We - // have to be certain this is safe even when this is an LCSSA PHI node. - // While the computed exit value is no longer varying in *this* loop, the - // exit block may be an exit block for an outer containing loop as well, - // the exit value may be varying in the outer loop, and thus it may still - // require an LCSSA PHI node. The safe case is when this is - // single-predecessor PHI node (LCSSA) and the exit block containing it is - // part of the enclosing loop, or this is the outer most loop of the nest. - // In either case the exit value could (at most) be varying in the same - // loop body as the phi node itself. Thus if it is in turn used outside of - // an enclosing loop it will only be via a separate LCSSA node. - bool LCSSASafePhiForRAUW = - NumPreds == 1 && - (!L->getParentLoop() || L->getParentLoop() == LI->getLoopFor(ExitBB)); - // Iterate over all of the PHI nodes. BasicBlock::iterator BBI = ExitBB->begin(); while ((PN = dyn_cast<PHINode>(BBI++))) { @@ -669,8 +653,7 @@ void IndVarSimplify::rewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) { } // Collect all the candidate PHINodes to be rewritten. - RewritePhiSet.emplace_back(PN, i, ExitVal, HighCost, - LCSSASafePhiForRAUW); + RewritePhiSet.emplace_back(PN, i, ExitVal, HighCost); } } } @@ -699,9 +682,9 @@ void IndVarSimplify::rewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) { if (isInstructionTriviallyDead(Inst, TLI)) DeadInsts.push_back(Inst); - // If we determined that this PHI is safe to replace even if an LCSSA - // PHI, do so. - if (Phi.SafePhi) { + // Replace PN with ExitVal if that is legal and does not break LCSSA. + if (PN->getNumIncomingValues() == 1 && + LI->replacementPreservesLCSSAForm(PN, ExitVal)) { PN->replaceAllUsesWith(ExitVal); PN->eraseFromParent(); } diff --git a/llvm/test/Transforms/IndVarSimplify/pr25576.ll b/llvm/test/Transforms/IndVarSimplify/pr25576.ll new file mode 100644 index 00000000000..c9ebc479535 --- /dev/null +++ b/llvm/test/Transforms/IndVarSimplify/pr25576.ll @@ -0,0 +1,31 @@ +; RUN: opt -S -indvars < %s | FileCheck %s + +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +define void @fn1() { +; CHECK-LABEL: @fn1( +entry: + br label %for.cond.loopexit + +for.cond.loopexit: ; preds = %for.inc7, %for.cond.loopexit, %entry + %c.1.lcssa = phi i32 [ %inc8, %for.inc7 ], [ 0, %for.cond.loopexit ], [ 0, %entry ] + br i1 undef, label %for.cond.loopexit, label %for.cond4.preheader + +for.cond4.preheader: ; preds = %for.inc7, %for.cond.loopexit + %c.17 = phi i32 [ %inc8, %for.inc7 ], [ 0, %for.cond.loopexit ] + br label %for.body6 + +for.body6: ; preds = %for.body6, %for.cond4.preheader + %inc14 = phi i32 [ 0, %for.cond4.preheader ], [ %inc, %for.body6 ] + %idxprom = zext i32 %inc14 to i64 + %inc = add i32 %inc14, 1 + %cmp5 = icmp ult i32 %inc, 2 + br i1 %cmp5, label %for.body6, label %for.inc7 + +for.inc7: ; preds = %for.body6 + %inc.lcssa = phi i32 [ %inc, %for.body6 ] + %inc8 = add i32 %c.17, 1 + %cmp = icmp ult i32 %inc8, %inc.lcssa + br i1 %cmp, label %for.cond4.preheader, label %for.cond.loopexit +} |
