[PATCH] D75620: [SimplifyCFG] Skip merging return blocks if it would break a CallBr.
Jonas Paulsson via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Mar 10 07:00:58 PDT 2020
This revision was automatically updated to reflect the committed changes.
Closed by commit rGc2dafe12dc24: [SimplifyCFG] Skip merging return blocks if it would break a CallBr. (authored by jonpa).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D75620/new/
https://reviews.llvm.org/D75620
Files:
llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
llvm/test/Transforms/SimplifyCFG/callbr-destinations.ll
Index: llvm/test/Transforms/SimplifyCFG/callbr-destinations.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/SimplifyCFG/callbr-destinations.ll
@@ -0,0 +1,28 @@
+; RUN: opt < %s -simplifycfg -disable-output
+;
+; Test that SimplifyCFG does not cause CallBr instructions to have duplicate
+; destinations, which will cause the verifier to assert.
+
+define void @fun0() {
+entry:
+ callbr void asm sideeffect "", "X"(i8* blockaddress(@fun0, %bb1))
+ to label %bb2 [label %bb1]
+
+bb1: ; preds = %bb
+ ret void
+
+bb2: ; preds = %bb
+ ret void
+}
+
+define void @fun1() {
+entry:
+ callbr void asm sideeffect "", "X"(i8* blockaddress(@fun1, %bb1))
+ to label %bb2 [label %bb1]
+
+bb2: ; preds = %bb
+ ret void
+
+bb1: ; preds = %bb
+ ret void
+}
Index: llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -104,6 +104,21 @@
continue;
}
+ // Skip merging if this would result in a CallBr instruction with a
+ // duplicate destination. FIXME: See note in CodeGenPrepare.cpp.
+ bool SkipCallBr = false;
+ for (pred_iterator PI = pred_begin(&BB), E = pred_end(&BB);
+ PI != E && !SkipCallBr; ++PI) {
+ if (auto *CBI = dyn_cast<CallBrInst>((*PI)->getTerminator()))
+ for (unsigned i = 0, e = CBI->getNumSuccessors(); i != e; ++i)
+ if (RetBlock == CBI->getSuccessor(i)) {
+ SkipCallBr = true;
+ break;
+ }
+ }
+ if (SkipCallBr)
+ continue;
+
// Otherwise, we found a duplicate return block. Merge the two.
Changed = true;
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