[PATCH] D64868: [SCEV] add NW flag for AddExpr (start + stride)

[ChenZheng via Phabricator via llvm-commits]

shchenz created this revision.
shchenz added reviewers: nikic, sanjoy, hfinkel, reames.
Herald added subscribers: llvm-commits, wuzish, javed.absar, hiraditya.
Herald added a project: LLVM.



  %i = phi i4 [ %start, %entry ], [ %i.next, %loop ]
  %i.next = add nsw i4 %i, %stride

If we know that `add` has `nsw` flag, then we get {%start, +, %stride} & {(start + stride), +, %stride} have `SCEV::FlagNSW`. We should also set (start+stride) with `SCEV::FlagNSW`.


https://reviews.llvm.org/D64868

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/limit-depth.ll
  llvm/test/Analysis/ScalarEvolution/nsw.ll
  llvm/test/Analysis/ScalarEvolution/trip-count12.ll
  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
@@ -179,7 +179,7 @@
 }
 
 ; CHECK: Determining loop execution counts for: @nsw_startx
-; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x) smax %n))
+; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x)<nsw> smax %n))
 ; CHECK: Loop %loop: max backedge-taken count is -1
 define void @nsw_startx(i4 %n, i4 %x) {
 entry:
@@ -195,7 +195,7 @@
 }
 
 ; CHECK: Determining loop execution counts for: @nsw_startx_step2
-; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x) smax %n)) /u 2)
+; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x)<nsw> smax %n)) /u 2)
 ; CHECK: Loop %loop: max backedge-taken count is 7
 define void @nsw_startx_step2(i4 %n, i4 %x) {
 entry:
@@ -381,7 +381,7 @@
 }
 
 ; CHECK: Determining loop execution counts for: @even_nsw_startx
-; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x) smax (2 * %n)))
+; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x)<nsw> smax (2 * %n)))
 ; CHECK: Loop %loop: max backedge-taken count is -2
 define void @even_nsw_startx(i4 %n, i4 %x) {
 entry:
@@ -398,7 +398,7 @@
 }
 
 ; CHECK: Determining loop execution counts for: @even_nsw_startx_step2
-; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x) smax (2 * %n))) /u 2)
+; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x)<nsw> smax (2 * %n))) /u 2)
 ; CHECK: Loop %loop: max backedge-taken count is 7
 define void @even_nsw_startx_step2(i4 %n, i4 %x) {
 entry:
Index: llvm/test/Analysis/ScalarEvolution/trip-count12.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/trip-count12.ll
+++ llvm/test/Analysis/ScalarEvolution/trip-count12.ll
@@ -1,7 +1,7 @@
 ; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
 
 ; CHECK: Determining loop execution counts for: @test
-; CHECK: Loop %for.body: backedge-taken count is ((-2 + %len) /u 2)
+; CHECK: Loop %for.body: backedge-taken count is ((-2 + %len)<nsw> /u 2)
 ; CHECK: Loop %for.body: max backedge-taken count is 1073741823
 
 define zeroext i16 @test(i16* nocapture %p, i32 %len) nounwind readonly {
Index: llvm/test/Analysis/ScalarEvolution/nsw.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/nsw.ll
+++ llvm/test/Analysis/ScalarEvolution/nsw.ll
@@ -163,7 +163,7 @@
 declare void @f(i32)
 
 ; CHECK-LABEL: nswnowrap
-; CHECK: --> {(1 + %v)<nsw>,+,1}<nsw><%for.body>{{ U: [^ ]+ S: [^ ]+}}{{ *}}Exits: (1 + ((1 + %v)<nsw> smax %v))
+; CHECK: --> {(1 + %v)<nsw>,+,1}<nsw><%for.body>{{ U: [^ ]+ S: [^ ]+}}{{ *}}Exits: (2 + %v)
 define void @nswnowrap(i32 %v, i32* %buf) {
 entry:
   %add = add nsw i32 %v, 1
Index: llvm/test/Analysis/ScalarEvolution/limit-depth.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/limit-depth.ll
+++ llvm/test/Analysis/ScalarEvolution/limit-depth.ll
@@ -46,7 +46,7 @@
 define void @test_sext(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f) {
 ; CHECK-LABEL: @test_sext
 ; CHECK:        %se2 = sext i64 %iv2.inc to i128
-; CHECK-NEXT:   -->  {(1 + (sext i64 {(sext i32 (1 + %a) to i64),+,1}<nsw><%loop> to i128))<nsw>,+,1}<nsw><%loop2>
+; CHECK-NEXT:   -->  {(1 + (sext i64 {(sext i32 (1 + %a)<nsw> to i64),+,1}<nsw><%loop> to i128))<nsw>,+,1}<nsw><%loop2>
 entry:
   br label %loop
 
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -4991,7 +4991,7 @@
   // overflow.
   if (auto *BEInst = dyn_cast<Instruction>(BEValueV))
     if (isLoopInvariant(Accum, L) && isAddRecNeverPoison(BEInst, L))
-      (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags);
+      (void)getAddRecExpr(getAddExpr(StartVal, Accum, Flags), Accum, L, Flags);
 
   return PHISCEV;
 }


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