[PATCH] D105941: [ScalarEvolution] Make isKnownNonZero handle more cases.

[Eli Friedman via Phabricator via llvm-commits]

efriedma created this revision.
efriedma added reviewers: reames, mkazantsev, nikic.
Herald added a subscriber: hiraditya.
efriedma requested review of this revision.
Herald added a project: LLVM.

Using an unsigned range instead of signed ranges is a bit more precise.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D105941

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/trip-count9.ll


Index: llvm/test/Analysis/ScalarEvolution/trip-count9.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/trip-count9.ll
+++ llvm/test/Analysis/ScalarEvolution/trip-count9.ll
@@ -311,9 +311,9 @@
 define void @even_start1(i4 %n) {
 ; CHECK-LABEL: 'even_start1'
 ; CHECK-NEXT:  Determining loop execution counts for: @even_start1
-; CHECK-NEXT:  Loop %loop: backedge-taken count is (-2 + (2 smax (2 * %n)))<nsw>
+; CHECK-NEXT:  Loop %loop: backedge-taken count is (-2 + (2 * %n))
 ; CHECK-NEXT:  Loop %loop: max backedge-taken count is 4
-; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is (-2 + (2 smax (2 * %n)))<nsw>
+; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is (-2 + (2 * %n))
 ; CHECK-NEXT:   Predicates:
 ; CHECK:       Loop %loop: Trip multiple is 1
 ;
@@ -333,9 +333,9 @@
 define void @even_start1_step2(i4 %n) {
 ; CHECK-LABEL: 'even_start1_step2'
 ; CHECK-NEXT:  Determining loop execution counts for: @even_start1_step2
-; CHECK-NEXT:  Loop %loop: backedge-taken count is ((-2 + (3 smax (2 * %n)))<nsw> /u 2)
+; CHECK-NEXT:  Loop %loop: backedge-taken count is ((-2 + (2 * %n)) /u 2)
 ; CHECK-NEXT:  Loop %loop: max backedge-taken count is 2
-; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is ((-2 + (3 smax (2 * %n)))<nsw> /u 2)
+; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is ((-2 + (2 * %n)) /u 2)
 ; CHECK-NEXT:   Predicates:
 ; CHECK:       Loop %loop: Trip multiple is 1
 ;
@@ -443,9 +443,9 @@
 define void @even_nsw_start1(i4 %n) {
 ; CHECK-LABEL: 'even_nsw_start1'
 ; CHECK-NEXT:  Determining loop execution counts for: @even_nsw_start1
-; CHECK-NEXT:  Loop %loop: backedge-taken count is (-2 + (2 smax (2 * %n)))<nsw>
+; CHECK-NEXT:  Loop %loop: backedge-taken count is (-2 + (2 * %n))
 ; CHECK-NEXT:  Loop %loop: max backedge-taken count is 4
-; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is (-2 + (2 smax (2 * %n)))<nsw>
+; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is (-2 + (2 * %n))
 ; CHECK-NEXT:   Predicates:
 ; CHECK:       Loop %loop: Trip multiple is 1
 ;
@@ -465,9 +465,9 @@
 define void @even_nsw_start1_step2(i4 %n) {
 ; CHECK-LABEL: 'even_nsw_start1_step2'
 ; CHECK-NEXT:  Determining loop execution counts for: @even_nsw_start1_step2
-; CHECK-NEXT:  Loop %loop: backedge-taken count is ((-2 + (3 smax (2 * %n)))<nsw> /u 2)
+; CHECK-NEXT:  Loop %loop: backedge-taken count is ((-2 + (2 * %n)) /u 2)
 ; CHECK-NEXT:  Loop %loop: max backedge-taken count is 2
-; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is ((-2 + (3 smax (2 * %n)))<nsw> /u 2)
+; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is ((-2 + (2 * %n)) /u 2)
 ; CHECK-NEXT:   Predicates:
 ; CHECK:       Loop %loop: Trip multiple is 1
 ;
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -9822,7 +9822,7 @@
 }
 
 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
-  return isKnownNegative(S) || isKnownPositive(S);
+  return getUnsignedRangeMin(S) != 0;
 }
 
 std::pair<const SCEV *, const SCEV *>


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