Skip to content

[ConstraintElim] Use cond from header as upper bound on IV in exit BB. #94610

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 4 commits into from
Jul 9, 2024
Merged

[ConstraintElim] Use cond from header as upper bound on IV in exit BB. #94610

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
8310ce6
[ConstraintElim] Use cond from header as upper bound on IV in exit BB.
fhahn Jun 6, 2024
474acb5
!fixup properly handle non-monotonically increasing case.
fhahn Jun 6, 2024
d51a036
!fixup always emit precondition, don't check unique predecessor
fhahn Jun 28, 2024
e1af9a5
Merge branch 'main' into ce-loop-header-exit
fhahn Jul 9, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
14 changes: 14 additions & 0 deletions llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1032,6 +1032,20 @@ void State::addInfoForInductions(BasicBlock &BB) {
WorkList.push_back(FactOrCheck::getConditionFact(
DTN, CmpInst::ICMP_SLT, PN, B,
ConditionTy(CmpInst::ICMP_SLE, StartValue, B)));

// Try to add condition from header to the exit blocks. When exiting either
// with EQ or NE in the header, we know that the induction value must be u<=
// B, as other exits may only exit earlier.
assert(!StepOffset.isNegative() && "induction must be increasing");
assert((Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_NE) &&
"unsupported predicate");
ConditionTy Precond = {CmpInst::ICMP_ULE, StartValue, B};
SmallVector<BasicBlock *> ExitBBs;
L->getExitBlocks(ExitBBs);
for (BasicBlock *EB : ExitBBs) {
WorkList.emplace_back(FactOrCheck::getConditionFact(
DT.getNode(EB), CmpInst::ICMP_ULE, A, B, Precond));
}
}

void State::addInfoFor(BasicBlock &BB) {
Expand Down
15 changes: 5 additions & 10 deletions llvm/test/Transforms/ConstraintElimination/induction-condition-in-loop-exit.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,7 @@ define i1 @multi_exiting_loop_eq_same_unique_exit_const_compare_known(ptr %s) {
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: br i1 [[LATCH_C]], label %[[LOOP_HEADER]], label %[[EXIT]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[T:%.*]] = icmp ult i32 [[IV]], 1235
; CHECK-NEXT: ret i1 [[T]]
; CHECK-NEXT: ret i1 true
;
entry:
br label %loop.header
Expand Down Expand Up @@ -99,8 +98,7 @@ define i1 @multi_exiting_loop_eq_same_unique_exit_const_compare_known_due_to_pre
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[LATCH_C]], label %[[LOOP_HEADER]], label %[[EXIT]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[T:%.*]] = icmp ult i32 [[IV]], 1235
; CHECK-NEXT: ret i1 [[T]]
; CHECK-NEXT: ret i1 true
;
entry:
%pre.c = icmp ule i32 %start, 1234
Expand Down Expand Up @@ -341,8 +339,7 @@ define i1 @multi_exiting_loop_eq_same_unique_exit_var_compare_known(ptr %s, i32
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: br i1 [[LATCH_C]], label %[[LOOP_HEADER]], label %[[EXIT]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[T:%.*]] = icmp ule i32 [[IV]], [[N]]
; CHECK-NEXT: ret i1 [[T]]
; CHECK-NEXT: ret i1 true
;
entry:
br label %loop.header
Expand Down Expand Up @@ -419,8 +416,7 @@ define i1 @multi_exiting_loop_ne_same_unique_exit_const_compare_known(ptr %s) {
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: br i1 [[LATCH_C]], label %[[LOOP_HEADER]], label %[[EXIT]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[T:%.*]] = icmp ult i32 [[IV]], 1235
; CHECK-NEXT: ret i1 [[T]]
; CHECK-NEXT: ret i1 true
;
entry:
br label %loop.header
Expand Down Expand Up @@ -545,8 +541,7 @@ define i1 @multi_exiting_loop_eq_different_exits_2_const_compare_known(ptr %s, i
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: br i1 [[LATCH_C]], label %[[LOOP_HEADER]], label %[[EXIT_2]]
; CHECK: [[EXIT_1]]:
; CHECK-NEXT: [[T_1:%.*]] = icmp ult i32 [[IV]], 1235
; CHECK-NEXT: ret i1 [[T_1]]
; CHECK-NEXT: ret i1 true
; CHECK: [[EXIT_2]]:
; CHECK-NEXT: ret i1 true
;
Expand Down
Loading