[llvm] 6af5f56 - [SCEV] Collect conditions from assumes same way as for branches.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Thu May 26 10:18:09 PDT 2022
Author: Florian Hahn
Date: 2022-05-26T18:17:13+01:00
New Revision: 6af5f5697c8560e09c305d5cfd74a7bda0d4d311
URL: https://github.com/llvm/llvm-project/commit/6af5f5697c8560e09c305d5cfd74a7bda0d4d311
DIFF: https://github.com/llvm/llvm-project/commit/6af5f5697c8560e09c305d5cfd74a7bda0d4d311.diff
LOG: [SCEV] Collect conditions from assumes same way as for branches.
Also collect conditions from assume up-front in applyLoopGuards.
This allows re-using the logic to handle logical ANDs as assume
conditions.
It should should pave the road for a fix for #55645.
Added:
Modified:
llvm/lib/Analysis/ScalarEvolution.cpp
llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index c8193732ea16d..59e1f5a0857cc 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -14518,12 +14518,23 @@ const SCEV *ScalarEvolution::applyLoopGuards(const SCEV *Expr, const Loop *L) {
ExprsToRewrite.push_back(LHS);
}
};
- // First, collect conditions from dominating branches. Starting at the loop
+
+ SmallVector<std::pair<Value *, bool>> Terms;
+ // First, collect information from assumptions dominating the loop.
+ for (auto &AssumeVH : AC.assumptions()) {
+ if (!AssumeVH)
+ continue;
+ auto *AssumeI = cast<CallInst>(AssumeVH);
+ if (!DT.dominates(AssumeI, L->getHeader()))
+ continue;
+ Terms.emplace_back(AssumeI->getOperand(0), true);
+ }
+
+ // Second, collect conditions from dominating branches. Starting at the loop
// predecessor, climb up the predecessor chain, as long as there are
// predecessors that can be found that have unique successors leading to the
// original header.
// TODO: share this logic with isLoopEntryGuardedByCond.
- SmallVector<std::pair<Value *, bool>> Terms;
for (std::pair<const BasicBlock *, const BasicBlock *> Pair(
L->getLoopPredecessor(), L->getHeader());
Pair.first; Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
@@ -14570,19 +14581,6 @@ const SCEV *ScalarEvolution::applyLoopGuards(const SCEV *Expr, const Loop *L) {
}
}
- // Also collect information from assumptions dominating the loop.
- for (auto &AssumeVH : AC.assumptions()) {
- if (!AssumeVH)
- continue;
- auto *AssumeI = cast<CallInst>(AssumeVH);
- auto *Cmp = dyn_cast<ICmpInst>(AssumeI->getOperand(0));
- if (!Cmp || !DT.dominates(AssumeI, L->getHeader()))
- continue;
- const auto *LHS = getSCEV(Cmp->getOperand(0));
- const auto *RHS = getSCEV(Cmp->getOperand(1));
- CollectCondition(Cmp->getPredicate(), LHS, RHS, RewriteMap);
- }
-
if (RewriteMap.empty())
return Expr;
diff --git a/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll b/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
index d8e95705c72d7..7ee5a0a622b1c 100644
--- a/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
+++ b/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
@@ -825,14 +825,14 @@ define void @test_guard_assume_and(i32* nocapture readonly %data, i64 %count) {
; CHECK-NEXT: %cmp.and = and i1 %cmp.ult, %cmp.ne
; CHECK-NEXT: --> (%cmp.ult umin %cmp.ne) U: full-set S: full-set
; CHECK-NEXT: %iv = phi i64 [ %iv.next, %loop ], [ 0, %entry ]
-; CHECK-NEXT: --> {0,+,1}<nuw><%loop> U: [0,-1) S: [0,-1) Exits: (-1 + %count) LoopDispositions: { %loop: Computable }
+; CHECK-NEXT: --> {0,+,1}<nuw><%loop> U: [0,4) S: [0,4) Exits: (-1 + %count) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %idx = getelementptr inbounds i32, i32* %data, i64 %iv
-; CHECK-NEXT: --> {%data,+,4}<%loop> U: full-set S: full-set Exits: (-4 + (4 * %count) + %data) LoopDispositions: { %loop: Computable }
+; CHECK-NEXT: --> {%data,+,4}<nuw><%loop> U: full-set S: full-set Exits: (-4 + (4 * %count) + %data) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = add nuw i64 %iv, 1
-; CHECK-NEXT: --> {1,+,1}<nuw><%loop> U: [1,0) S: [1,0) Exits: %count LoopDispositions: { %loop: Computable }
+; CHECK-NEXT: --> {1,+,1}<nuw><%loop> U: [1,5) S: [1,5) Exits: %count LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @test_guard_assume_and
; CHECK-NEXT: Loop %loop: backedge-taken count is (-1 + %count)
-; CHECK-NEXT: Loop %loop: max backedge-taken count is -2
+; CHECK-NEXT: Loop %loop: max backedge-taken count is 3
; CHECK-NEXT: Loop %loop: Predicated backedge-taken count is (-1 + %count)
; CHECK-NEXT: Predicates:
; CHECK: Loop %loop: Trip multiple is 1
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