add test, address comments

Author: akshayrdeodhar

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -6031,7 +6031,7 @@ const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) {
 const SCEV *
 ScalarEvolution::createNodeForPHIWithIdenticalOperands(PHINode *PN) {
   BinaryOperator *CommonInst = nullptr;
-  // check if instructions are identical
+  // Check if instructions are identical.
   for (Value *Incoming : PN->incoming_values()) {
     auto *IncomingInst = dyn_cast<BinaryOperator>(Incoming);
     if (!IncomingInst)
@@ -6047,10 +6047,9 @@ ScalarEvolution::createNodeForPHIWithIdenticalOperands(PHINode *PN) {
   if (!CommonInst)
     return nullptr;
 
-  // check if SCEV exprs for instructions are identical
+  // Check if SCEV exprs for instructions are identical.
   const SCEV *CommonSCEV = getSCEV(CommonInst);
-  bool SCEVExprsIdentical = std::all_of(
-      PN->incoming_values().begin(), PN->incoming_values().end(),
+  bool SCEVExprsIdentical = all_of(drop_begin(PN->incoming_values()),
       [this, CommonSCEV](Value *V) { return CommonSCEV == getSCEV(V); });
   return SCEVExprsIdentical ? CommonSCEV : nullptr;
 }

llvm/test/Analysis/ScalarEvolution/trip-count-phi-increment.ll

@@ -1,8 +1,8 @@
 ; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 5
 ; RUN: opt < %s -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck %s
-define void @test(ptr %x, ptr %y) {
-; CHECK-LABEL: 'test'
-; CHECK-NEXT:  Classifying expressions for: @test
+define void @test1(ptr %x, ptr %y) {
+; CHECK-LABEL: 'test1'
+; CHECK-NEXT:  Classifying expressions for: @test1
 ; CHECK-NEXT:    %v1.0 = phi i32 [ 0, %entry ], [ %k.0, %if.end ]
 ; CHECK-NEXT:    --> {0,+,1}<nuw><nsw><%for.cond> U: [0,7) S: [0,7) Exits: 6 LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %add = add nsw i32 %v1.0, 1
@@ -11,7 +11,7 @@ define void @test(ptr %x, ptr %y) {
 ; CHECK-NEXT:    --> {1,+,1}<nuw><nsw><%for.cond> U: [1,8) S: [1,8) Exits: 7 LoopDispositions: { %for.cond: Computable }
 ; CHECK-NEXT:    %k.0 = phi i32 [ %add, %if.then ], [ %add6, %if.else ]
 ; CHECK-NEXT:    --> {1,+,1}<nuw><nsw><%for.cond> U: [1,8) S: [1,8) Exits: 7 LoopDispositions: { %for.cond: Computable }
-; CHECK-NEXT:  Determining loop execution counts for: @test
+; CHECK-NEXT:  Determining loop execution counts for: @test1
 ; CHECK-NEXT:  Loop %for.cond: backedge-taken count is i32 6
 ; CHECK-NEXT:  Loop %for.cond: constant max backedge-taken count is i32 6
 ; CHECK-NEXT:  Loop %for.cond: symbolic max backedge-taken count is i32 6
@@ -44,3 +44,49 @@ if.end:                                                ; preds = %4, %3
 exit:                                                ; preds = %5
   ret void
 }
+
+define void @test2(ptr %x, ptr %y) {
+; CHECK-LABEL: 'test2'
+; CHECK-NEXT:  Classifying expressions for: @test2
+; CHECK-NEXT:    %v1.0 = phi i32 [ 0, %entry ], [ %k.0, %if.end ]
+; CHECK-NEXT:    --> {0,+,1}<nuw><nsw><%for.cond> U: [0,7) S: [0,7) Exits: 6 LoopDispositions: { %for.cond: Computable }
+; CHECK-NEXT:    %add = add nuw i32 %v1.0, 1
+; CHECK-NEXT:    --> {1,+,1}<nuw><nsw><%for.cond> U: [1,8) S: [1,8) Exits: 7 LoopDispositions: { %for.cond: Computable }
+; CHECK-NEXT:    %add6 = add nsw i32 %v1.0, 1
+; CHECK-NEXT:    --> {1,+,1}<nuw><nsw><%for.cond> U: [1,8) S: [1,8) Exits: 7 LoopDispositions: { %for.cond: Computable }
+; CHECK-NEXT:    %k.0 = phi i32 [ %add, %if.then ], [ %add6, %if.else ]
+; CHECK-NEXT:    --> {1,+,1}<nuw><nsw><%for.cond> U: [1,8) S: [1,8) Exits: 7 LoopDispositions: { %for.cond: Computable }
+; CHECK-NEXT:  Determining loop execution counts for: @test2
+; CHECK-NEXT:  Loop %for.cond: backedge-taken count is i32 6
+; CHECK-NEXT:  Loop %for.cond: constant max backedge-taken count is i32 6
+; CHECK-NEXT:  Loop %for.cond: symbolic max backedge-taken count is i32 6
+; CHECK-NEXT:  Loop %for.cond: Trip multiple is 7
+;
+entry:
+  br label %for.cond
+
+for.cond:                                                ; preds = %6, %0
+  %v1.0 = phi i32 [ 0, %entry ], [ %k.0, %if.end ]
+  %cmp = icmp slt i32 %v1.0, 6
+  br i1 %cmp, label %for.body, label %exit
+
+for.body:                                                ; preds = %1
+  %cmp3 = icmp slt i32 %v1.0, 2
+  br i1 %cmp3, label %if.then, label %if.else
+
+if.then:                                                ; preds = %2
+  %add = add nuw i32 %v1.0, 1
+  br label %if.end
+
+if.else:                                                ; preds = %2
+  %add6 = add nsw i32 %v1.0, 1
+  br label %if.end
+
+if.end:                                                ; preds = %4, %3
+  %k.0 = phi i32 [ %add, %if.then ], [ %add6, %if.else ]
+  br label %for.cond
+
+exit:                                                ; preds = %5
+  ret void
+}
+