diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp --- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp +++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp @@ -2117,7 +2117,7 @@ // unconditional branch, we should be merging PredBB and BB instead. For // simplicity, we don't deal with a switch. BranchInst *PredBBBranch = dyn_cast(PredBB->getTerminator()); - if (!PredBBBranch) + if (!PredBBBranch || PredBBBranch->isUnconditional()) return false; // If PredBB has exactly one incoming edge, we don't gain anything by copying diff --git a/llvm/test/Transforms/JumpThreading/thread-two-bbs6.ll b/llvm/test/Transforms/JumpThreading/thread-two-bbs6.ll new file mode 100644 --- /dev/null +++ b/llvm/test/Transforms/JumpThreading/thread-two-bbs6.ll @@ -0,0 +1,42 @@ +;; Test that we can handle unconditional PredBB when threading jumps through two +;; successive basic blocks. +; RUN: opt -S -passes='function(jump-threading)' < %s | FileCheck %s + +target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +define i32 @f(i32* %0) { +; CHECK-LABEL: @f +; CHECK: br i1 %good, label %pred.bb, label %pred.pred.bb +entry: + %size = call i64 @get_size(i32* %0) + %good = icmp ugt i64 %size, 3 + br i1 %good, label %pred.bb, label %pred.pred.bb + +; CHECK: pred.pred.bb: +; CHECK: br label %pred.bb +; CHECK: pred.bb: +; CHECK: br label %bb +; CHECK: bb: +pred.pred.bb: ; preds = %entry + call void @effect() + br label %pred.bb +pred.bb: ; preds = %pred.pred.bb, %entry + %v = load i32, i32* %0 + br label %bb + +bb: ; preds = %pred.bb + call void @effect1(i8* blockaddress(@f, %bb)) + br i1 %good, label %cont2, label %cont1 + +cont1: ; preds = %bb + br i1 %good, label %exit, label %cont2 +cont2: ; preds = %bb + br label %exit +exit: ; preds = %cont1, %cont2 + ret i32 %v +} + +declare i64 @get_size(i32*) +declare void @effect() +declare void @effect1(i8*)