[llvm] r335816 - [IndVarSimplify] Ignore unreachable users of truncs

[Max Kazantsev via llvm-commits]

Author: mkazantsev
Date: Thu Jun 28 01:20:03 2018
New Revision: 335816

URL: http://llvm.org/viewvc/llvm-project?rev=335816&view=rev
Log:
[IndVarSimplify] Ignore unreachable users of truncs

If a trunc has a user in a block which is not reachable from entry,
we can safely perform trunc elimination as if this user didn't exist.

Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
    llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp?rev=335816&r1=335815&r2=335816&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp Thu Jun 28 01:20:03 2018
@@ -535,6 +535,10 @@ bool SimplifyIndvar::eliminateTrunc(Trun
   // Bail if we find something different.
   SmallVector<ICmpInst *, 4> ICmpUsers;
   for (auto *U : TI->users()) {
+    // We don't care about users in unreachable blocks.
+    if (isa<Instruction>(U) &&
+        !DT->isReachableFromEntry(cast<Instruction>(U)->getParent()))
+      continue;
     if (ICmpInst *ICI = dyn_cast<ICmpInst>(U)) {
       if (ICI->getOperand(0) == TI && L->isLoopInvariant(ICI->getOperand(1))) {
         assert(L->contains(ICI->getParent()) && "LCSSA form broken?");

Modified: llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll?rev=335816&r1=335815&r2=335816&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll Thu Jun 28 01:20:03 2018
@@ -484,3 +484,50 @@ loop:
 exit:
   ret void
 }
+
+define void @test_11() {
+; CHECK-LABEL: @test_11(
+; CHECK-NEXT:    br label [[BB1:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    br i1 undef, label [[BB2:%.*]], label [[BB6:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    br i1 undef, label [[BB3:%.*]], label [[BB4:%.*]]
+; CHECK:       bb3:
+; CHECK-NEXT:    br label [[BB4]]
+; CHECK:       bb4:
+; CHECK-NEXT:    br label [[BB6]]
+; CHECK:       bb5:
+; CHECK-NEXT:    [[_TMP24:%.*]] = icmp slt i16 undef, 0
+; CHECK-NEXT:    br i1 [[_TMP24]], label [[BB5:%.*]], label [[BB5]]
+; CHECK:       bb6:
+; CHECK-NEXT:    br i1 false, label [[BB1]], label [[BB7:%.*]]
+; CHECK:       bb7:
+; CHECK-NEXT:    ret void
+;
+  br label %bb1
+
+bb1:                                              ; preds = %bb6, %0
+  %e.5.0 = phi i32 [ 0, %0 ], [ %_tmp32, %bb6 ]
+  br i1 undef, label %bb2, label %bb6
+
+bb2:                                              ; preds = %bb1
+  %_tmp15 = trunc i32 %e.5.0 to i16
+  br i1 undef, label %bb3, label %bb4
+
+bb3:                                              ; preds = %bb2
+  br label %bb4
+
+bb4:                                              ; preds = %bb3, %bb2
+  br label %bb6
+
+bb5:                                              ; preds = %bb5, %bb5
+  %_tmp24 = icmp slt i16 %_tmp15, 0
+  br i1 %_tmp24, label %bb5, label %bb5
+
+bb6:                                              ; preds = %bb4, %bb1
+  %_tmp32 = add nuw nsw i32 %e.5.0, 1
+  br i1 false, label %bb1, label %bb7
+
+bb7:                                             ; preds = %bb6
+  ret void
+}