[llvm] da9f2ba - [SCEV] Reorder operands checks in collectConditions.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Thu Nov 18 01:36:49 PST 2021
Author: Florian Hahn
Date: 2021-11-18T09:36:16Z
New Revision: da9f2ba3b1a6ffddc548ff8da16ca882ef5bb716
URL: https://github.com/llvm/llvm-project/commit/da9f2ba3b1a6ffddc548ff8da16ca882ef5bb716
DIFF: https://github.com/llvm/llvm-project/commit/da9f2ba3b1a6ffddc548ff8da16ca882ef5bb716.diff
LOG: [SCEV] Reorder operands checks in collectConditions.
The initial two cases require a SCEVConstant as RHS. Pull up the condition
to check and swap SCEVConstants from below. Also remove a redundant
check & swap if RHS is SCEVUnknown.
Added:
Modified:
llvm/lib/Analysis/ScalarEvolution.cpp
llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
llvm/test/Analysis/ScalarEvolution/trip-multiple-guard-info.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 29988d05919b..649e49dda843 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -13774,26 +13774,8 @@ const SCEV *ScalarEvolution::applyLoopGuards(const SCEV *Expr, const Loop *L) {
// SCEV. In particular, using contextual facts to imply flags is *NOT*
// legal. See the scoping rules for flags in the header to understand why.
- // If we have LHS == 0, check if LHS is computing a property of some unknown
- // SCEV %v which we can rewrite %v to express explicitly.
- const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
- if (Predicate == CmpInst::ICMP_EQ && RHSC &&
- RHSC->getValue()->isNullValue()) {
- // If LHS is A % B, i.e. A % B == 0, rewrite A to (A /u B) * B to
- // explicitly express that.
- const SCEV *URemLHS = nullptr;
- const SCEV *URemRHS = nullptr;
- if (matchURem(LHS, URemLHS, URemRHS)) {
- if (const SCEVUnknown *LHSUnknown = dyn_cast<SCEVUnknown>(URemLHS)) {
- auto Multiple = getMulExpr(getUDivExpr(URemLHS, URemRHS), URemRHS);
- RewriteMap[LHSUnknown] = Multiple;
- ExprsToRewrite.push_back(LHSUnknown);
- return;
- }
- }
- }
-
- if (!isa<SCEVUnknown>(LHS) && isa<SCEVUnknown>(RHS)) {
+ // If LHS is a constant, apply information to the other expression.
+ if (isa<SCEVConstant>(LHS)) {
std::swap(LHS, RHS);
Predicate = CmpInst::getSwappedPredicate(Predicate);
}
@@ -13831,20 +13813,35 @@ const SCEV *ScalarEvolution::applyLoopGuards(const SCEV *Expr, const Loop *L) {
if (MatchRangeCheckIdiom())
return;
- // If RHS is SCEVUnknown, make sure the information is applied to it.
- if (isa<SCEVUnknown>(RHS)) {
- std::swap(LHS, RHS);
- Predicate = CmpInst::getSwappedPredicate(Predicate);
- }
- // If LHS is a constant, apply information to the other expression.
- if (isa<SCEVConstant>(LHS)) {
- std::swap(LHS, RHS);
- Predicate = CmpInst::getSwappedPredicate(Predicate);
+ // If we have LHS == 0, check if LHS is computing a property of some unknown
+ // SCEV %v which we can rewrite %v to express explicitly.
+ const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
+ if (Predicate == CmpInst::ICMP_EQ && RHSC &&
+ RHSC->getValue()->isNullValue()) {
+ // If LHS is A % B, i.e. A % B == 0, rewrite A to (A /u B) * B to
+ // explicitly express that.
+ const SCEV *URemLHS = nullptr;
+ const SCEV *URemRHS = nullptr;
+ if (matchURem(LHS, URemLHS, URemRHS)) {
+ if (const SCEVUnknown *LHSUnknown = dyn_cast<SCEVUnknown>(URemLHS)) {
+ auto Multiple = getMulExpr(getUDivExpr(URemLHS, URemRHS), URemRHS);
+ RewriteMap[LHSUnknown] = Multiple;
+ ExprsToRewrite.push_back(LHSUnknown);
+ return;
+ }
+ }
}
+
// Do not apply information for constants or if RHS contains an AddRec.
if (isa<SCEVConstant>(LHS) || containsAddRecurrence(RHS))
return;
+ // If RHS is SCEVUnknown, make sure the information is applied to it.
+ if (!isa<SCEVUnknown>(LHS) && isa<SCEVUnknown>(RHS)) {
+ std::swap(LHS, RHS);
+ Predicate = CmpInst::getSwappedPredicate(Predicate);
+ }
+
// Limit to expressions that can be rewritten.
if (!isa<SCEVUnknown>(LHS) && !isa<SCEVZeroExtendExpr>(LHS))
return;
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 3026f94da8fc..38ea8b5dfbab 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
@@ -1295,14 +1295,14 @@ define void @optimized_range_check_unsigned_icmp_ops_swapped(i16* %pred, i32 %N)
; CHECK-NEXT: %N.off = add i32 %N, -1
; CHECK-NEXT: --> (-1 + %N) U: full-set S: full-set
; CHECK-NEXT: %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
-; CHECK-NEXT: --> {0,+,1}<nuw><nsw><%loop> U: [0,-2147483648) S: [0,-2147483648) Exits: (-1 + %N) LoopDispositions: { %loop: Computable }
+; CHECK-NEXT: --> {0,+,1}<nuw><nsw><%loop> U: [0,7) S: [0,7) Exits: (-1 + %N) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %gep = getelementptr inbounds i16, i16* %pred, i32 %iv
; CHECK-NEXT: --> {%pred,+,2}<nuw><%loop> U: full-set S: full-set Exits: ((2 * (zext i32 (-1 + %N) to i64))<nuw><nsw> + %pred) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = add nuw nsw i32 %iv, 1
-; CHECK-NEXT: --> {1,+,1}<nuw><nsw><%loop> U: [1,-2147483648) S: [1,-2147483648) Exits: %N LoopDispositions: { %loop: Computable }
+; CHECK-NEXT: --> {1,+,1}<nuw><nsw><%loop> U: [1,8) S: [1,8) Exits: %N LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @optimized_range_check_unsigned_icmp_ops_swapped
; CHECK-NEXT: Loop %loop: backedge-taken count is (-1 + %N)
-; CHECK-NEXT: Loop %loop: max backedge-taken count is -1
+; CHECK-NEXT: Loop %loop: max backedge-taken count is 6
; CHECK-NEXT: Loop %loop: Predicated backedge-taken count is (-1 + %N)
; CHECK-NEXT: Predicates:
; CHECK: Loop %loop: Trip multiple is 1
diff --git a/llvm/test/Analysis/ScalarEvolution/trip-multiple-guard-info.ll b/llvm/test/Analysis/ScalarEvolution/trip-multiple-guard-info.ll
index 1c99ccf3fa73..8b16899c7e08 100644
--- a/llvm/test/Analysis/ScalarEvolution/trip-multiple-guard-info.ll
+++ b/llvm/test/Analysis/ScalarEvolution/trip-multiple-guard-info.ll
@@ -34,7 +34,7 @@ define void @test_trip_multiple_4_icmp_ops_swapped(i32 %num) {
; CHECK: Loop %for.body: backedge-taken count is (-1 + %num)
; CHECK-NEXT: Loop %for.body: max backedge-taken count is -2
; CHECK-NEXT: Loop %for.body: Predicated backedge-taken count is (-1 + %num)
-; CHECK: Loop %for.body: Trip multiple is 1
+; CHECK: Loop %for.body: Trip multiple is 4
;
entry:
%u = urem i32 %num, 4
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