[llvm] r348426 - Revert r347934 "[SCEV] Guard movement of insertion point for loop-invariants"
David L. Jones via llvm-commits
llvm-commits at lists.llvm.org
Wed Dec 5 15:13:50 PST 2018
Author: dlj
Date: Wed Dec 5 15:13:50 2018
New Revision: 348426
URL: http://llvm.org/viewvc/llvm-project?rev=348426&view=rev
Log:
Revert r347934 "[SCEV] Guard movement of insertion point for loop-invariants"
This change caused SEGVs in instcombine. (The r347934 change seems to me to be a
precipitating cause, not a root cause. Details are on the llvm-commits thread
for r347934.)
Removed:
llvm/trunk/test/Transforms/LoopVectorize/pr30806.ll
Modified:
llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp
Modified: llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp?rev=348426&r1=348425&r2=348426&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolutionExpander.cpp Wed Dec 5 15:13:50 2018
@@ -1732,50 +1732,49 @@ Value *SCEVExpander::expand(const SCEV *
// Compute an insertion point for this SCEV object. Hoist the instructions
// as far out in the loop nest as possible.
Instruction *InsertPt = &*Builder.GetInsertPoint();
-
- // We can move insertion point only if there is no div or rem operations
- // otherwise we are risky to move it over the check for zero denominator.
- auto SafeToHoist = [](const SCEV *S) {
- return !SCEVExprContains(S, [](const SCEV *S) {
- if (const auto *D = dyn_cast<SCEVUDivExpr>(S)) {
- if (const auto *SC = dyn_cast<SCEVConstant>(D->getRHS()))
- // Division by non-zero constants can be hoisted.
- return SC->getValue()->isZero();
- // All other divisions should not be moved as they may be
- // divisions by zero and should be kept within the
- // conditions of the surrounding loops that guard their
- // execution (see PR35406).
- return true;
- }
- return false;
- });
- };
- if (SafeToHoist(S)) {
- for (Loop *L = SE.LI.getLoopFor(Builder.GetInsertBlock());;
- L = L->getParentLoop()) {
- if (SE.isLoopInvariant(S, L)) {
- if (!L) break;
- if (BasicBlock *Preheader = L->getLoopPreheader())
- InsertPt = Preheader->getTerminator();
- else
- // LSR sets the insertion point for AddRec start/step values to the
- // block start to simplify value reuse, even though it's an invalid
- // position. SCEVExpander must correct for this in all cases.
- InsertPt = &*L->getHeader()->getFirstInsertionPt();
- } else {
- // If the SCEV is computable at this level, insert it into the header
- // after the PHIs (and after any other instructions that we've inserted
- // there) so that it is guaranteed to dominate any user inside the loop.
- if (L && SE.hasComputableLoopEvolution(S, L) && !PostIncLoops.count(L))
- InsertPt = &*L->getHeader()->getFirstInsertionPt();
- while (InsertPt->getIterator() != Builder.GetInsertPoint() &&
- (isInsertedInstruction(InsertPt) ||
- isa<DbgInfoIntrinsic>(InsertPt)))
- InsertPt = &*std::next(InsertPt->getIterator());
- break;
+ for (Loop *L = SE.LI.getLoopFor(Builder.GetInsertBlock());;
+ L = L->getParentLoop())
+ if (SE.isLoopInvariant(S, L)) {
+ if (!L) break;
+ if (BasicBlock *Preheader = L->getLoopPreheader())
+ InsertPt = Preheader->getTerminator();
+ else {
+ // LSR sets the insertion point for AddRec start/step values to the
+ // block start to simplify value reuse, even though it's an invalid
+ // position. SCEVExpander must correct for this in all cases.
+ InsertPt = &*L->getHeader()->getFirstInsertionPt();
+ }
+ } else {
+ // We can move insertion point only if there is no div or rem operations
+ // otherwise we are risky to move it over the check for zero denominator.
+ auto SafeToHoist = [](const SCEV *S) {
+ return !SCEVExprContains(S, [](const SCEV *S) {
+ if (const auto *D = dyn_cast<SCEVUDivExpr>(S)) {
+ if (const auto *SC = dyn_cast<SCEVConstant>(D->getRHS()))
+ // Division by non-zero constants can be hoisted.
+ return SC->getValue()->isZero();
+ // All other divisions should not be moved as they may be
+ // divisions by zero and should be kept within the
+ // conditions of the surrounding loops that guard their
+ // execution (see PR35406).
+ return true;
+ }
+ return false;
+ });
+ };
+ // If the SCEV is computable at this level, insert it into the header
+ // after the PHIs (and after any other instructions that we've inserted
+ // there) so that it is guaranteed to dominate any user inside the loop.
+ if (L && SE.hasComputableLoopEvolution(S, L) && !PostIncLoops.count(L) &&
+ SafeToHoist(S))
+ InsertPt = &*L->getHeader()->getFirstInsertionPt();
+ while (InsertPt->getIterator() != Builder.GetInsertPoint() &&
+ (isInsertedInstruction(InsertPt) ||
+ isa<DbgInfoIntrinsic>(InsertPt))) {
+ InsertPt = &*std::next(InsertPt->getIterator());
}
+ break;
}
- }
// Check to see if we already expanded this here.
auto I = InsertedExpressions.find(std::make_pair(S, InsertPt));
Removed: llvm/trunk/test/Transforms/LoopVectorize/pr30806.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/pr30806.ll?rev=348425&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/pr30806.ll (original)
+++ llvm/trunk/test/Transforms/LoopVectorize/pr30806.ll (removed)
@@ -1,65 +0,0 @@
-; RUN: opt -loop-vectorize -S < %s 2>&1 | FileCheck %s
-
-; Produced from test-case:
-;
-; void testGuardedInnerLoop(uint32_t *ptr, uint32_t denom, uint32_t numer, uint32_t outer_lim)
-; {
-; for(uint32_t outer_i = 0; outer_i < outer_lim; ++outer_i) {
-; if (denom > 0) {
-; const uint32_t lim = numer / denom;
-;
-; for (uint32_t i = 0; i < lim; ++i)
-; ptr[i] = 1;
-; }
-; }
-; }
-
-
-target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
-target triple = "x86_64-unknown-linux-gnu"
-
-define void @testGuardedInnerLoop(i32* %ptr, i32 %denom, i32 %numer, i32 %outer_lim) {
-entry:
- %cmp1 = icmp eq i32 %outer_lim, 0
- br i1 %cmp1, label %exit, label %loop1.preheader
-
-; Verify that a 'udiv' does not appear between the 'loop1.preheader' label, and
-; whatever label comes next.
-loop1.preheader:
-; CHECK-LABEL: loop1.preheader:
-; CHECK-NOT: udiv
-; CHECK-LABEL: :
- br label %loop1
-
-loop1:
- %outer_i = phi i32 [ %inc1, %loop2.exit ], [ 0, %loop1.preheader ]
- %0 = add i32 %denom, -1
- %1 = icmp ult i32 %0, %numer
- br i1 %1, label %loop2.preheader, label %loop2.exit
-
-; Verify that a 'udiv' does appear between the 'loop2.preheader' label, and
-; whatever label comes next.
-loop2.preheader:
-; CHECK-LABEL: loop2.preheader:
-; CHECK: udiv
-; CHECK-LABEL: :
- %lim = udiv i32 %numer, %denom
- %2 = zext i32 %lim to i64
- br label %loop2
-
-loop2:
- %indvar.loop2 = phi i64 [ 0, %loop2.preheader ], [ %indvar.loop2.next, %loop2 ]
- %arrayidx = getelementptr inbounds i32, i32* %ptr, i64 %indvar.loop2
- store i32 1, i32* %arrayidx, align 4
- %indvar.loop2.next = add nuw nsw i64 %indvar.loop2, 1
- %cmp2 = icmp ult i64 %indvar.loop2.next, %2
- br i1 %cmp2, label %loop2, label %loop2.exit
-
-loop2.exit:
- %inc1 = add nuw i32 %outer_i, 1
- %exitcond = icmp eq i32 %inc1, %outer_lim
- br i1 %exitcond, label %exit, label %loop1
-
-exit:
- ret void
-}
More information about the llvm-commits
mailing list