[PATCH] D101196: [SCEV] Handle uge/ugt predicates in applyLoopGuards()

[Nikita Popov via Phabricator via llvm-commits]

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

These can be handled the same way as ule/ult, just using umax instead of umin. This is useful in cases where the umax prevents the upper bound from overflowing.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D101196

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll


Index: llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
+++ llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
@@ -586,12 +586,12 @@
 ; CHECK-NEXT:    %shr = lshr i32 %blockSize, 2
 ; CHECK-NEXT:    --> (%blockSize /u 4) U: [0,1073741824) S: [0,1073741824)
 ; CHECK-NEXT:    %iv = phi i32 [ %dec, %while.body ], [ %shr, %while.body.preheader ]
-; CHECK-NEXT:    --> {(%blockSize /u 4),+,-1}<%while.body> U: full-set S: full-set Exits: 1 LoopDispositions: { %while.body: Computable }
+; CHECK-NEXT:    --> {(%blockSize /u 4),+,-1}<%while.body> U: [-1073741822,1073741824) S: [-1073741822,1073741824) Exits: 1 LoopDispositions: { %while.body: Computable }
 ; CHECK-NEXT:    %dec = add i32 %iv, -1
-; CHECK-NEXT:    --> {(-1 + (%blockSize /u 4))<nsw>,+,-1}<%while.body> U: full-set S: full-set Exits: 0 LoopDispositions: { %while.body: Computable }
+; CHECK-NEXT:    --> {(-1 + (%blockSize /u 4))<nsw>,+,-1}<%while.body> U: [-1073741823,1073741823) S: [-1073741823,1073741823) Exits: 0 LoopDispositions: { %while.body: Computable }
 ; CHECK-NEXT:  Determining loop execution counts for: @test_guard_uge
 ; CHECK-NEXT:  Loop %while.body: backedge-taken count is (-1 + (%blockSize /u 4))<nsw>
-; CHECK-NEXT:  Loop %while.body: max backedge-taken count is -1
+; CHECK-NEXT:  Loop %while.body: max backedge-taken count is 1073741822
 ; CHECK-NEXT:  Loop %while.body: Predicated backedge-taken count is (-1 + (%blockSize /u 4))<nsw>
 ; CHECK-NEXT:   Predicates:
 ; CHECK:       Loop %while.body: Trip multiple is 1
@@ -622,12 +622,12 @@
 ; CHECK-NEXT:    %shr = lshr i32 %blockSize, 2
 ; CHECK-NEXT:    --> (%blockSize /u 4) U: [0,1073741824) S: [0,1073741824)
 ; CHECK-NEXT:    %iv = phi i32 [ %dec, %while.body ], [ %shr, %while.body.preheader ]
-; CHECK-NEXT:    --> {(%blockSize /u 4),+,-1}<%while.body> U: full-set S: full-set Exits: 1 LoopDispositions: { %while.body: Computable }
+; CHECK-NEXT:    --> {(%blockSize /u 4),+,-1}<%while.body> U: [-1073741822,1073741824) S: [-1073741822,1073741824) Exits: 1 LoopDispositions: { %while.body: Computable }
 ; CHECK-NEXT:    %dec = add i32 %iv, -1
-; CHECK-NEXT:    --> {(-1 + (%blockSize /u 4))<nsw>,+,-1}<%while.body> U: full-set S: full-set Exits: 0 LoopDispositions: { %while.body: Computable }
+; CHECK-NEXT:    --> {(-1 + (%blockSize /u 4))<nsw>,+,-1}<%while.body> U: [-1073741823,1073741823) S: [-1073741823,1073741823) Exits: 0 LoopDispositions: { %while.body: Computable }
 ; CHECK-NEXT:  Determining loop execution counts for: @test_guard_ugt
 ; CHECK-NEXT:  Loop %while.body: backedge-taken count is (-1 + (%blockSize /u 4))<nsw>
-; CHECK-NEXT:  Loop %while.body: max backedge-taken count is -1
+; CHECK-NEXT:  Loop %while.body: max backedge-taken count is 1073741822
 ; CHECK-NEXT:  Loop %while.body: Predicated backedge-taken count is (-1 + (%blockSize /u 4))<nsw>
 ; CHECK-NEXT:   Predicates:
 ; CHECK:       Loop %while.body: Trip multiple is 1
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -13457,6 +13457,27 @@
       }
       break;
     }
+    case CmpInst::ICMP_UGT:  {
+      if (!containsAddRecurrence(RHS)) {
+        const SCEV *Base = LHS;
+        auto I = RewriteMap.find(LHSUnknown->getValue());
+        if (I != RewriteMap.end())
+          Base = I->second;
+        RewriteMap[LHSUnknown->getValue()] =
+            getUMaxExpr(Base, getAddExpr(RHS, getOne(RHS->getType())));
+      }
+      break;
+    }
+    case CmpInst::ICMP_UGE:  {
+      if (!containsAddRecurrence(RHS)) {
+        const SCEV *Base = LHS;
+        auto I = RewriteMap.find(LHSUnknown->getValue());
+        if (I != RewriteMap.end())
+          Base = I->second;
+        RewriteMap[LHSUnknown->getValue()] = getUMaxExpr(Base, RHS);
+      }
+      break;
+    }
     case CmpInst::ICMP_EQ:
       if (isa<SCEVConstant>(RHS))
         RewriteMap[LHSUnknown->getValue()] = RHS;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D101196.340145.patch
Type: text/x-patch
Size: 4174 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20210423/96fedf78/attachment.bin>