[llvm] r324204 - Re-apply [SCEV] Fix isLoopEntryGuardedByCond usage
Serguei Katkov via llvm-commits
llvm-commits at lists.llvm.org
Sun Feb 4 21:49:47 PST 2018
Author: skatkov
Date: Sun Feb 4 21:49:47 2018
New Revision: 324204
URL: http://llvm.org/viewvc/llvm-project?rev=324204&view=rev
Log:
Re-apply [SCEV] Fix isLoopEntryGuardedByCond usage
ScalarEvolution::isKnownPredicate invokes isLoopEntryGuardedByCond without check
that SCEV is available at entry point of the loop. It is incorrect and fixed by patch.
To bugs additionally fixed:
assert is moved after the check whether loop is not a nullptr.
Usage of isLoopEntryGuardedByCond in ScalarEvolution::isImpliedCondOperandsViaNoOverflow
is guarded by isAvailableAtLoopEntry.
Reviewers: sanjoy, mkazantsev, anna, dorit, reames
Reviewed By: mkazantsev
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D42417
Added:
llvm/trunk/test/Transforms/IndVarSimplify/inner-loop.ll
Modified:
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=324204&r1=324203&r2=324204&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Sun Feb 4 21:49:47 2018
@@ -8669,7 +8669,8 @@ bool ScalarEvolution::isKnownPredicate(I
bool RightGuarded = false;
if (LAR) {
const Loop *L = LAR->getLoop();
- if (isLoopEntryGuardedByCond(L, Pred, LAR->getStart(), RHS) &&
+ if (isAvailableAtLoopEntry(RHS, L) &&
+ isLoopEntryGuardedByCond(L, Pred, LAR->getStart(), RHS) &&
isLoopBackedgeGuardedByCond(L, Pred, LAR->getPostIncExpr(*this), RHS)) {
if (!RAR) return true;
LeftGuarded = true;
@@ -8677,7 +8678,8 @@ bool ScalarEvolution::isKnownPredicate(I
}
if (RAR) {
const Loop *L = RAR->getLoop();
- if (isLoopEntryGuardedByCond(L, Pred, LHS, RAR->getStart()) &&
+ if (isAvailableAtLoopEntry(LHS, L) &&
+ isLoopEntryGuardedByCond(L, Pred, LHS, RAR->getStart()) &&
isLoopBackedgeGuardedByCond(L, Pred, LHS, RAR->getPostIncExpr(*this))) {
if (!LAR) return true;
RightGuarded = true;
@@ -9062,6 +9064,12 @@ ScalarEvolution::isLoopEntryGuardedByCon
// (interprocedural conditions notwithstanding).
if (!L) return false;
+ // Both LHS and RHS must be available at loop entry.
+ assert(isAvailableAtLoopEntry(LHS, L) &&
+ "LHS is not available at Loop Entry");
+ assert(isAvailableAtLoopEntry(RHS, L) &&
+ "RHS is not available at Loop Entry");
+
if (isKnownPredicateViaConstantRanges(Pred, LHS, RHS))
return true;
@@ -9418,7 +9426,8 @@ bool ScalarEvolution::isImpliedCondOpera
}
// Try to prove (1) or (2), as needed.
- return isLoopEntryGuardedByCond(L, Pred, FoundRHS,
+ return isAvailableAtLoopEntry(FoundRHS, L) &&
+ isLoopEntryGuardedByCond(L, Pred, FoundRHS,
getConstant(FoundRHSLimit));
}
Modified: llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp?rev=324204&r1=324203&r2=324204&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp Sun Feb 4 21:49:47 2018
@@ -934,9 +934,9 @@ LoopStructure::parseLoopStructure(Scalar
return None;
}
- if (!SE.isLoopEntryGuardedByCond(
- &L, BoundPred, IndVarStart,
- SE.getAddExpr(RightSCEV, Step))) {
+ if (!SE.isAvailableAtLoopEntry(RightSCEV, &L) ||
+ !SE.isLoopEntryGuardedByCond(&L, BoundPred, IndVarStart,
+ SE.getAddExpr(RightSCEV, Step))) {
FailureReason = "Induction variable start not bounded by upper limit";
return None;
}
@@ -948,7 +948,8 @@ LoopStructure::parseLoopStructure(Scalar
RightValue = B.CreateAdd(RightValue, One);
}
} else {
- if (!SE.isLoopEntryGuardedByCond(&L, BoundPred, IndVarStart, RightSCEV)) {
+ if (!SE.isAvailableAtLoopEntry(RightSCEV, &L) ||
+ !SE.isLoopEntryGuardedByCond(&L, BoundPred, IndVarStart, RightSCEV)) {
FailureReason = "Induction variable start not bounded by upper limit";
return None;
}
@@ -1014,9 +1015,10 @@ LoopStructure::parseLoopStructure(Scalar
return None;
}
- if (!SE.isLoopEntryGuardedByCond(
- &L, BoundPred, IndVarStart,
- SE.getMinusSCEV(RightSCEV, SE.getOne(RightSCEV->getType())))) {
+ if (!SE.isAvailableAtLoopEntry(RightSCEV, &L) ||
+ !SE.isLoopEntryGuardedByCond(
+ &L, BoundPred, IndVarStart,
+ SE.getMinusSCEV(RightSCEV, SE.getOne(RightSCEV->getType())))) {
FailureReason = "Induction variable start not bounded by lower limit";
return None;
}
@@ -1028,7 +1030,8 @@ LoopStructure::parseLoopStructure(Scalar
RightValue = B.CreateSub(RightValue, One);
}
} else {
- if (!SE.isLoopEntryGuardedByCond(&L, BoundPred, IndVarStart, RightSCEV)) {
+ if (!SE.isAvailableAtLoopEntry(RightSCEV, &L) ||
+ !SE.isLoopEntryGuardedByCond(&L, BoundPred, IndVarStart, RightSCEV)) {
FailureReason = "Induction variable start not bounded by lower limit";
return None;
}
Added: llvm/trunk/test/Transforms/IndVarSimplify/inner-loop.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/inner-loop.ll?rev=324204&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/inner-loop.ll (added)
+++ llvm/trunk/test/Transforms/IndVarSimplify/inner-loop.ll Sun Feb 4 21:49:47 2018
@@ -0,0 +1,54 @@
+; RUN: opt < %s -indvars -S | FileCheck %s
+
+; This is regression test for the bug in ScalarEvolution::isKnownPredicate.
+; It does not check whether SCEV is available at loop entry before invoking
+; and utility function isLoopEntryGuardedByCond and that leads to miscompile.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare void @foo(i64)
+declare void @bar(i32)
+
+define void @test(i8* %arr) {
+entry:
+ br label %outer_header
+
+outer_header:
+ %i = phi i32 [40, %entry], [%i.next, %outer_latch]
+ %i.64 = sext i32 %i to i64
+ br label %inner_header
+
+inner_header:
+ %j = phi i32 [27, %outer_header], [%j.next, %inner_backedge]
+ %j1 = zext i32 %j to i64
+; The next 4 lines are required for avoid widening of %j and
+; SCEV at %cmp would not be AddRec.
+ %gep = getelementptr inbounds i8, i8* %arr, i64 %j1
+ %ld = load i8, i8* %gep
+ %ec = icmp eq i8 %ld, 0
+ br i1 %ec, label %return, label %inner_backedge
+
+inner_backedge:
+ %cmp = icmp ult i32 %j, %i
+ %s = select i1 %cmp, i32 %i, i32 %j
+; Select should not be simplified because if
+; %i == 26 and %j == 27, %s should be equal to %j.
+; In case of a bug the instruction is simplified to
+; %s = select i1 true, i32 %0, i32 %j
+; CHECK-NOT: %s = select i1 true
+ call void @bar(i32 %s)
+ %j.next = add nsw i32 %j, -2
+ %cond = icmp ult i32 %j, 3
+ br i1 %cond, label %outer_latch, label %inner_header
+
+outer_latch:
+ %i.next = add i32 %i, -1
+ %cond2 = icmp sgt i32 %i.next, 13
+; This line is just for forcing widening of %i
+ call void @foo(i64 %i.64)
+ br i1 %cond2, label %outer_header, label %return
+
+return:
+ ret void
+}
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