[PATCH] D132356: [SimplifyCFG] Don't widen cond br to cond br if false branch has successors

[Dmitry Makogon via Phabricator via llvm-commits]

dmakogon updated this revision to Diff 454730.
dmakogon added a comment.

Hoisted the condition, added comments & updated test to not branch on undef but on a normal value


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132356/new/

https://reviews.llvm.org/D132356

Files:
  llvm/lib/Transforms/Utils/SimplifyCFG.cpp
  llvm/test/Transforms/SimplifyCFG/pr52290.ll


Index: llvm/test/Transforms/SimplifyCFG/pr52290.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/pr52290.ll
+++ llvm/test/Transforms/SimplifyCFG/pr52290.ll
@@ -1,15 +1,29 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -simplifycfg -S | FileCheck %s
 ; RUN: opt < %s -passes=simplifycfg -S | FileCheck %s
 
-; XFAIL: *
-; REQUIRES: asserts
-; FIXME: Fails due to infinite loop in iterativelySimplifyCFG.
-
 ; ModuleID = 'test/Transforms/SimplifyCFG/pr-new.ll'
 source_filename = "test/Transforms/SimplifyCFG/pr-new.ll"
 
 define i32 @test(float %arg, i1 %c) gc "statepoint-example" personality i32* ()* @blam {
-; CHECK-LABEL: @test
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[TMP:%.*]] = call i1 @llvm.experimental.widenable.condition()
+; CHECK-NEXT:    br i1 [[TMP]], label [[BB2:%.*]], label [[BB1:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[BB7:%.*]], label [[BB5:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr inbounds i8, i8 addrspace(1)* undef, i64 16
+; CHECK-NEXT:    br i1 [[C]], label [[BB7]], label [[BB4:%.*]]
+; CHECK:       bb4:
+; CHECK-NEXT:    call void @snork() [ "deopt"() ]
+; CHECK-NEXT:    unreachable
+; CHECK:       bb5:
+; CHECK-NEXT:    ret i32 0
+; CHECK:       bb7:
+; CHECK-NEXT:    [[TMP8:%.*]] = call i32 (...) @llvm.experimental.deoptimize.i32(i32 10) [ "deopt"() ]
+; CHECK-NEXT:    ret i32 [[TMP8]]
+;
 bb:
   %tmp = call i1 @llvm.experimental.widenable.condition()
   br i1 %tmp, label %bb2, label %bb1
Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -3999,6 +3999,12 @@
     return false;
   if (!IfFalseBB->phis().empty())
     return false; // TODO
+  // This helps avoid infinite loop with other transformations in SimplifyCFG,
+  // e.g. SimplifyCondBranchToCondBranch which may do the opposite thing to what
+  // is done here.
+  // TODO: There might be a more fine-grained solution to this.
+  if (llvm::succ_empty(IfFalseBB))
+    return false;
   // Use lambda to lazily compute expensive condition after cheap ones.
   auto NoSideEffects = [](BasicBlock &BB) {
     return llvm::none_of(BB, [](const Instruction &I) {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D132356.454730.patch
Type: text/x-patch
Size: 2408 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220823/d1ad9dcd/attachment.bin>