[PATCH] D113578: [SCEV] Apply loop guards when computing max BTC for arbitrary steps.
Florian Hahn via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Nov 12 04:23:05 PST 2021
fhahn updated this revision to Diff 386803.
fhahn added a comment.
Replace over-aggressive assertion with selecting the minimum max BTC. Added test case where the assert is voilated in 69c1cbe20f5d <https://reviews.llvm.org/rG69c1cbe20f5db9b7a3b7086acabd92db1cd59cad>.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D113578/new/
https://reviews.llvm.org/D113578
Files:
llvm/lib/Analysis/ScalarEvolution.cpp
llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info-rewrite-expressions.ll
Index: llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info-rewrite-expressions.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info-rewrite-expressions.ll
+++ llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info-rewrite-expressions.ll
@@ -67,9 +67,9 @@
; Test case from PR52464.
define i32 @rewrite_zext_icmp_ne(i32 %N) {
; CHECK-LABEL: Determining loop execution counts for: @rewrite_zext_icmp_ne
-; CHECK-NEXT: Loop %loop: backedge-taken count is ((-4 + (4 * ((4 + (zext i32 (-1 + (zext i2 (trunc i32 %N to i2) to i32))<nsw> to i64))<nuw><nsw> /u 4))<nuw><nsw>)<nsw> /u 4)
-; CHECK-NEXT: Loop %loop: max backedge-taken count is 1073741823
-; CHECK-NEXT: Loop %loop: Predicated backedge-taken count is ((-4 + (4 * ((4 + (zext i32 (-1 + (zext i2 (trunc i32 %N to i2) to i32))<nsw> to i64))<nuw><nsw> /u 4))<nuw><nsw>)<nsw> /u 4)
+; CHECK-NEXT: Loop %loop: backedge-taken count is 0
+; CHECK-NEXT: Loop %loop: max backedge-taken count is 0
+; CHECK-NEXT: Loop %loop: Predicated backedge-taken count is 0
; CHECK-NEXT: Predicates:
; CHECK-EMPTY:
; CHECK-NEXT: Loop %loop: Trip multiple is 1
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -9656,9 +9656,12 @@
// Solve the general equation.
const SCEV *E = SolveLinEquationWithOverflow(StepC->getAPInt(),
getNegativeSCEV(Start), *this);
- const SCEV *M = E == getCouldNotCompute()
- ? E
- : getConstant(getUnsignedRangeMax(E));
+
+ const SCEV *M = E;
+ if (E != getCouldNotCompute()) {
+ APInt MaxWithGuards = getUnsignedRangeMax(applyLoopGuards(E, L));
+ M = getConstant(APIntOps::umin(MaxWithGuards, getUnsignedRangeMax(E)));
+ }
return ExitLimit(E, M, false, Predicates);
}
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D113578.386803.patch
Type: text/x-patch
Size: 2033 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20211112/50e6d90f/attachment.bin>
More information about the llvm-commits
mailing list