[PATCH] D109786: [SCEV] (udiv X, Y) * Y is always NUW

[Philip Reames via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG9bdb19cca292: [SCEV] (udiv X, Y) * Y is always NUW (authored by reames).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D109786/new/

https://reviews.llvm.org/D109786

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/extract-highbits-variablemask.ll
  llvm/test/Analysis/ScalarEvolution/max-be-count-not-constant.ll
  llvm/test/Analysis/ScalarEvolution/mul.ll


Index: llvm/test/Analysis/ScalarEvolution/mul.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/mul.ll
+++ llvm/test/Analysis/ScalarEvolution/mul.ll
@@ -7,7 +7,7 @@
 ; CHECK-NEXT:    %udiv = udiv i8 %x, %y
 ; CHECK-NEXT:    --> (%x /u %y) U: full-set S: full-set
 ; CHECK-NEXT:    %res = mul i8 %udiv, %y
-; CHECK-NEXT:    --> ((%x /u %y) * %y) U: full-set S: full-set
+; CHECK-NEXT:    --> ((%x /u %y) * %y)<nuw> U: full-set S: full-set
 ; CHECK-NEXT:  Determining loop execution counts for: @test
 ;
   %udiv = udiv i8 %x, %y
@@ -65,7 +65,7 @@
 ; CHECK-NEXT:    %udiv = udiv i8 %x, %y
 ; CHECK-NEXT:    --> (%x /u (trunc i32 %y32 to i8)) U: full-set S: full-set
 ; CHECK-NEXT:    %res = mul i8 %udiv, %y
-; CHECK-NEXT:    --> ((trunc i32 %y32 to i8) * (%x /u (trunc i32 %y32 to i8))) U: full-set S: full-set
+; CHECK-NEXT:    --> ((trunc i32 %y32 to i8) * (%x /u (trunc i32 %y32 to i8)))<nuw> U: full-set S: full-set
 ; CHECK-NEXT:  Determining loop execution counts for: @test5
 ;
   %y = trunc i32 %y32 to i8
Index: llvm/test/Analysis/ScalarEvolution/max-be-count-not-constant.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/max-be-count-not-constant.ll
+++ llvm/test/Analysis/ScalarEvolution/max-be-count-not-constant.ll
@@ -16,9 +16,9 @@
 ; CHECK-NEXT:    %tmp1 = add nsw i32 %tmp, 2
 ; CHECK-NEXT:    --> (2 + %tmp)<nsw> U: [1,3) S: [1,3)
 ; CHECK-NEXT:    %tmp3 = phi i32 [ 0, %bb ], [ %tmp4, %bb2 ]
-; CHECK-NEXT:    --> {0,+,(2 + %tmp)<nsw>}<nuw><nsw><%bb2> U: [0,3) S: [0,3) Exits: ((2 + %tmp)<nsw> * (1 /u (2 + %tmp)<nsw>)) LoopDispositions: { %bb2: Computable }
+; CHECK-NEXT:    --> {0,+,(2 + %tmp)<nsw>}<nuw><nsw><%bb2> U: [0,3) S: [0,3) Exits: ((2 + %tmp)<nsw> * (1 /u (2 + %tmp)<nsw>))<nuw> LoopDispositions: { %bb2: Computable }
 ; CHECK-NEXT:    %tmp4 = add nuw nsw i32 %tmp1, %tmp3
-; CHECK-NEXT:    --> {(2 + %tmp)<nsw>,+,(2 + %tmp)<nsw>}<nuw><nsw><%bb2> U: [1,5) S: [1,5) Exits: (2 + ((2 + %tmp)<nsw> * (1 /u (2 + %tmp)<nsw>)) + %tmp) LoopDispositions: { %bb2: Computable }
+; CHECK-NEXT:    --> {(2 + %tmp)<nsw>,+,(2 + %tmp)<nsw>}<nuw><nsw><%bb2> U: [1,5) S: [1,5) Exits: (2 + ((2 + %tmp)<nsw> * (1 /u (2 + %tmp)<nsw>))<nuw> + %tmp) LoopDispositions: { %bb2: Computable }
 ; CHECK-NEXT:  Determining loop execution counts for: @pluto
 ; CHECK-NEXT:  Loop %bb2: backedge-taken count is (1 /u (2 + %tmp)<nsw>)
 ; CHECK-NEXT:  Loop %bb2: max backedge-taken count is 1
Index: llvm/test/Analysis/ScalarEvolution/extract-highbits-variablemask.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/extract-highbits-variablemask.ll
+++ llvm/test/Analysis/ScalarEvolution/extract-highbits-variablemask.ll
@@ -10,7 +10,7 @@
 ; CHECK-NEXT:    %tmp1 = udiv i32 %val, %num
 ; CHECK-NEXT:    -->  (%val /u %num) U: full-set S: full-set
 ; CHECK-NEXT:    %tmp2 = mul i32 %tmp1, %num
-; CHECK-NEXT:    -->  ((%val /u %num) * %num) U: full-set S: full-set
+; CHECK-NEXT:    -->  ((%val /u %num) * %num)<nuw> U: full-set S: full-set
 ; CHECK-NEXT:  Determining loop execution counts for: @div
 ;
   %tmp1 = udiv i32 %val, %num
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -2397,6 +2397,17 @@
       Ops[0]->isZero() && IsKnownNonNegative(Ops[1]))
     Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
 
+  // both (udiv X, Y) * Y and Y * (udiv X, Y) are always NUW
+  if (Type == scMulExpr && !ScalarEvolution::hasFlags(Flags, SCEV::FlagNUW) &&
+      Ops.size() == 2) {
+    if (auto *UDiv = dyn_cast<SCEVUDivExpr>(Ops[0]))
+      if (UDiv->getOperand(1) == Ops[1])
+        Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
+    if (auto *UDiv = dyn_cast<SCEVUDivExpr>(Ops[1]))
+      if (UDiv->getOperand(1) == Ops[0])
+        Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
+  }
+
   return Flags;
 }
 


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