[PATCH] D58853: [SCEV] Handle case where MaxBECount is less precise than ExactBECount for OR.

[Florian Hahn via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL355259: [SCEV] Handle case where MaxBECount is less precise than ExactBECount for OR. (authored by fhahn, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D58853?vs=188994&id=189021#toc

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D58853/new/

https://reviews.llvm.org/D58853

Files:
  llvm/trunk/lib/Analysis/ScalarEvolution.cpp
  llvm/trunk/test/Analysis/ScalarEvolution/exact-exit-count-more-precise.ll
  llvm/trunk/test/Transforms/IndVarSimplify/pr26207.ll


Index: llvm/trunk/test/Analysis/ScalarEvolution/exact-exit-count-more-precise.ll
===================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/exact-exit-count-more-precise.ll
+++ llvm/trunk/test/Analysis/ScalarEvolution/exact-exit-count-more-precise.ll
@@ -0,0 +1,49 @@
+; RUN: opt -analyze -scalar-evolution %s | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @test_and(i16 %in) {
+  br label %bb2
+
+bb2:                                              ; preds = %bb1.i, %bb2, %0
+  %_tmp44.i = icmp slt i16 %in, 2
+  br i1 %_tmp44.i, label %bb1.i, label %bb2
+
+bb1.i:                                            ; preds = %bb1.i, %bb2
+  %_tmp25.i = phi i16 [ %in, %bb2 ], [ %_tmp6.i, %bb1.i ]
+  %_tmp6.i = add nsw i16 %_tmp25.i, 1
+  %_tmp10.i = icmp sge i16 %_tmp6.i, 2
+  %exitcond.i = icmp eq i16 %_tmp6.i, 2
+  %or.cond = and i1 %_tmp10.i, %exitcond.i
+  br i1 %or.cond, label %bb2, label %bb1.i
+}
+
+; CHECK-LABEL: Determining loop execution counts for: @test_and
+; CHECK-NEXT: Loop %bb1.i: backedge-taken count is (1 + (-1 * %in))
+; CHECK-NEXT: Loop %bb1.i: max backedge-taken count is -1
+; CHECK-NEXT: Loop %bb1.i: Predicated backedge-taken count is (1 + (-1 * %in))
+
+
+define void @test_or() {
+  %C10 = icmp slt i1 undef, undef
+  br i1 %C10, label %BB, label %exit
+
+BB:                                               ; preds = %BB, %0
+  %indvars.iv = phi i64 [ -1, %BB ], [ -1, %0 ]
+  %sum.01 = phi i32 [ %2, %BB ], [ undef, %0 ]
+  %1 = trunc i64 %indvars.iv to i32
+  %2 = add nsw i32 %1, %sum.01
+  %B3 = add i32 %1, %2
+  %C11 = icmp ult i32 %2, %1
+  %C5 = icmp sle i32 %1, %B3
+  %B = or i1 %C5, %C11
+  br i1 %B, label %BB, label %exit
+
+exit:                                      ; preds = %BB, %0
+  ret void
+}
+
+; CHECK-LABEL: Determining loop execution counts for: @test_or
+; CHECK-NEXT: Loop %BB: backedge-taken count is undef
+; CHECK-NEXT: Loop %BB: max backedge-taken count is -1
+; CHECK-NEXT: Loop %BB: Predicated backedge-taken count is undef
Index: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp
@@ -7272,6 +7272,14 @@
         if (EL0.ExactNotTaken == EL1.ExactNotTaken)
           BECount = EL0.ExactNotTaken;
       }
+      // There are cases (e.g. PR26207) where computeExitLimitFromCond is able
+      // to be more aggressive when computing BECount than when computing
+      // MaxBECount.  In these cases it is possible for EL0.ExactNotTaken and
+      // EL1.ExactNotTaken to match, but for EL0.MaxNotTaken and EL1.MaxNotTaken
+      // to not.
+      if (isa<SCEVCouldNotCompute>(MaxBECount) &&
+          !isa<SCEVCouldNotCompute>(BECount))
+        MaxBECount = getConstant(getUnsignedRangeMax(BECount));
 
       return ExitLimit(BECount, MaxBECount, false,
                        {&EL0.Predicates, &EL1.Predicates});
Index: llvm/trunk/test/Transforms/IndVarSimplify/pr26207.ll
===================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/pr26207.ll
+++ llvm/trunk/test/Transforms/IndVarSimplify/pr26207.ll
@@ -1,20 +0,0 @@
-; RUN: opt -S -indvars < %s | FileCheck %s
-
-target triple = "x86_64-unknown-linux-gnu"
-
-define void @main(i16 %in) {
-; CHECK-LABEL: @main(
-  br label %bb2
-
-bb2:                                              ; preds = %bb1.i, %bb2, %0
-  %_tmp44.i = icmp slt i16 %in, 2
-  br i1 %_tmp44.i, label %bb1.i, label %bb2
-
-bb1.i:                                            ; preds = %bb1.i, %bb2
-  %_tmp25.i = phi i16 [ %in, %bb2 ], [ %_tmp6.i, %bb1.i ]
-  %_tmp6.i = add nsw i16 %_tmp25.i, 1
-  %_tmp10.i = icmp sge i16 %_tmp6.i, 2
-  %exitcond.i = icmp eq i16 %_tmp6.i, 2
-  %or.cond = and i1 %_tmp10.i, %exitcond.i
-  br i1 %or.cond, label %bb2, label %bb1.i
-}


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