[PATCH] D82721: [ScalarEvolution] createSCEV(): MatchBinaryOp(): recognize `urem` disguised as an `srem`

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri updated this revision to Diff 274203.
lebedev.ri marked 2 inline comments as done.
lebedev.ri added a comment.

Addressing review notes:

- Sink into `createSCEV()`
- Use SCEV's `isKnownNonNegative()`
- Also handle `sdiv`


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D82721/new/

https://reviews.llvm.org/D82721

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/sdiv.ll
  llvm/test/Analysis/ScalarEvolution/srem.ll


Index: llvm/test/Analysis/ScalarEvolution/srem.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/srem.ll
+++ llvm/test/Analysis/ScalarEvolution/srem.ll
@@ -14,11 +14,11 @@
 ; CHECK-NEXT:    %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
 ; CHECK-NEXT:    --> {0,+,1}<nuw><nsw><%for.cond> U: [0,-2147483648) S: [0,-2147483648) Exits: %width LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %rem = srem i32 %i.0, 2
-; CHECK-NEXT:    --> %rem U: [0,2) S: [-2,2) Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
+; CHECK-NEXT:    --> (zext i1 {false,+,true}<%for.cond> to i32) U: [0,2) S: [0,2) Exits: (zext i1 (trunc i32 %width to i1) to i32) LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %idxprom = sext i32 %rem to i64
-; CHECK-NEXT:    --> (sext i32 %rem to i64) U: [0,2) S: [-2,2) Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
+; CHECK-NEXT:    --> (zext i1 {false,+,true}<%for.cond> to i64) U: [0,2) S: [0,2) Exits: (zext i1 (trunc i32 %width to i1) to i64) LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %arrayidx = getelementptr inbounds [2 x i32], [2 x i32]* %storage, i64 0, i64 %idxprom
-; CHECK-NEXT:    --> ((4 * (sext i32 %rem to i64))<nuw><nsw> + %storage)<nsw> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
+; CHECK-NEXT:    --> ((4 * (zext i1 {false,+,true}<%for.cond> to i64))<nuw><nsw> + %storage)<nsw> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: ((4 * (zext i1 (trunc i32 %width to i1) to i64))<nuw><nsw> + %storage)<nsw> LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %1 = load i32, i32* %arrayidx, align 4
 ; CHECK-NEXT:    --> %1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
 ; CHECK-NEXT:    %call = call i32 @_Z3adji(i32 %1)
Index: llvm/test/Analysis/ScalarEvolution/sdiv.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/sdiv.ll
+++ llvm/test/Analysis/ScalarEvolution/sdiv.ll
@@ -14,11 +14,11 @@
 ; CHECK-NEXT:    %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
 ; CHECK-NEXT:    --> {0,+,1}<nuw><nsw><%for.cond> U: [0,-2147483648) S: [0,-2147483648) Exits: %width LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %rem = sdiv i32 %i.0, 2
-; CHECK-NEXT:    --> (zext i1 {false,+,true}<%for.cond> to i32) U: [0,2) S: [0,2) Exits: (zext i1 (trunc i32 %width to i1) to i32) LoopDispositions: { %for.cond: Computable }
+; CHECK-NEXT:    --> ({0,+,1}<nuw><nsw><%for.cond> /u 2) U: [0,1073741824) S: [0,1073741824) Exits: (%width /u 2) LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %idxprom = sext i32 %rem to i64
-; CHECK-NEXT:    --> (zext i1 {false,+,true}<%for.cond> to i64) U: [0,2) S: [0,2) Exits: (zext i1 (trunc i32 %width to i1) to i64) LoopDispositions: { %for.cond: Computable }
+; CHECK-NEXT:    --> ({0,+,1}<nuw><nsw><%for.cond> /u 2) U: [0,2147483648) S: [0,2147483648) Exits: ((zext i32 %width to i64) /u 2) LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %arrayidx = getelementptr inbounds [2 x i32], [2 x i32]* %storage, i64 0, i64 %idxprom
-; CHECK-NEXT:    --> ((4 * (zext i1 {false,+,true}<%for.cond> to i64))<nuw><nsw> + %storage)<nsw> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: ((4 * (zext i1 (trunc i32 %width to i1) to i64))<nuw><nsw> + %storage)<nsw> LoopDispositions: { %for.cond: Computable }
+; CHECK-NEXT:    --> ((4 * ({0,+,1}<nuw><nsw><%for.cond> /u 2))<nuw><nsw> + %storage)<nsw> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: ((4 * ((zext i32 %width to i64) /u 2))<nuw><nsw> + %storage)<nsw> LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %1 = load i32, i32* %arrayidx, align 4
 ; CHECK-NEXT:    --> %1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
 ; CHECK-NEXT:    %call = call i32 @_Z3adji(i32 %1)
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -6303,6 +6303,20 @@
       return getSCEV(U->getOperand(0));
     break;
 
+  case Instruction::SDiv:
+    // If both operands are non-negative, this is just an udiv.
+    if (isKnownNonNegative(getSCEV(U->getOperand(0))) &&
+        isKnownNonNegative(getSCEV(U->getOperand(1))))
+      return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(U->getOperand(1)));
+    break;
+
+  case Instruction::SRem:
+    // If both operands are non-negative, this is just an urem.
+    if (isKnownNonNegative(getSCEV(U->getOperand(0))) &&
+        isKnownNonNegative(getSCEV(U->getOperand(1))))
+      return getURemExpr(getSCEV(U->getOperand(0)), getSCEV(U->getOperand(1)));
+    break;
+
   // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
   // lead to pointer expressions which cannot safely be expanded to GEPs,
   // because ScalarEvolution doesn't respect the GEP aliasing rules when


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D82721.274203.patch
Type: text/x-patch
Size: 5124 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20200629/2f4f3190/attachment.bin>