[PATCH] D51581: [IndVars] Strengthen restricton in rewriteLoopExitValues

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev updated this revision to Diff 170598.
mkazantsev marked an inline comment as done.
mkazantsev added a comment.

Fixed comment. All style rework can be done in follow-up, provided that the dependent pass is going to isolate this code into a separate method.


https://reviews.llvm.org/D51581

Files:
  lib/Transforms/Scalar/IndVarSimplify.cpp
  test/Transforms/IndVarSimplify/dont-recompute.ll


Index: test/Transforms/IndVarSimplify/dont-recompute.ll
===================================================================
--- test/Transforms/IndVarSimplify/dont-recompute.ll
+++ test/Transforms/IndVarSimplify/dont-recompute.ll
@@ -97,3 +97,29 @@
   tail call void @func(i32 %add)
   ret void
 }
+
+; CHECK-LABEL: @test4(
+define void @test4(i32 %m) nounwind uwtable {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %i.06 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %a.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
+  %add = add i32 %a.05, %m
+; CHECK: tail call void @func(i32 %add)
+  tail call void @func(i32 %add)
+  %inc = add nsw i32 %i.06, 1
+  %exitcond = icmp eq i32 %inc, 186
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+; CHECK: for.end:
+; CHECK-NOT: mul i32 %m, 186
+; CHECK:%add.lcssa = phi i32 [ %add, %for.body ]
+; CHECK-NEXT: %soft_use = add i32 %add.lcssa, 123
+; CHECK-NEXT: tail call void @func(i32 %soft_use)
+  %soft_use = add i32 %add, 123
+  tail call void @func(i32 %soft_use)
+  ret void
+}
Index: lib/Transforms/Scalar/IndVarSimplify.cpp
===================================================================
--- lib/Transforms/Scalar/IndVarSimplify.cpp
+++ lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -595,41 +595,20 @@
             !isSafeToExpand(ExitValue, *SE))
           continue;
 
-        // Computing the value outside of the loop brings no benefit if :
-        //  - it is definitely used inside the loop in a way which can not be
-        //    optimized away.
-        //  - no use outside of the loop can take advantage of hoisting the
-        //    computation out of the loop
+        // Computing the value outside of the loop brings no benefit if it is
+        // definitely used inside the loop in a way which can not be optimized
+        // away.
         if (ExitValue->getSCEVType()>=scMulExpr) {
           bool HasHardInternalUses = false;
-          bool HasSoftExternalUses = false;
           for (auto *IB : Inst->users()) {
             Instruction *UseInstr = cast<Instruction>(IB);
             unsigned Opc = UseInstr->getOpcode();
-            if (L->contains(UseInstr)) {
-              if (Opc == Instruction::Call)
-                HasHardInternalUses = true;
-            } else {
-              if (Opc == Instruction::PHI) {
-                // Do not count the Phi as a use. LCSSA may have inserted
-                // plenty of trivial ones.
-                for (auto *PB : UseInstr->users()) {
-                  unsigned PhiOpc = cast<Instruction>(PB)->getOpcode();
-                  if (PhiOpc != Instruction::Call &&
-                      PhiOpc != Instruction::Ret) {
-                    HasSoftExternalUses = true;
-                    break;
-                  }
-                }
-                continue;
-              }
-              if (Opc != Instruction::Call && Opc != Instruction::Ret) {
-                HasSoftExternalUses = true;
-                break;
-              }
+            if (L->contains(UseInstr) && Opc == Instruction::Call) {
+              HasHardInternalUses = true;
+              break;
             }
           }
-          if (HasHardInternalUses && !HasSoftExternalUses)
+          if (HasHardInternalUses)
             continue;
         }
 


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