Author: Sanjay Patel Date: 2020-12-02T13:39:33-05:00 New Revision: 9d6d24c25056c17db56cf1ef5124f82eb18afc2c
URL: https://github.com/llvm/llvm-project/commit/9d6d24c25056c17db56cf1ef5124f82eb18afc2c DIFF: https://github.com/llvm/llvm-project/commit/9d6d24c25056c17db56cf1ef5124f82eb18afc2c.diff LOG: [JumpThreading][VectorUtils] avoid infinite loop on unreachable IR https://llvm.org/PR48362 It's possible that we could stub this out sooner somewhere within JumpThreading, but I'm not sure how to do that, and then we would still have potential danger in other callers. I can't find a way to trigger this using 'instsimplify', however, because that already has a bailout on unreachable blocks. Added: Modified: llvm/lib/Analysis/VectorUtils.cpp llvm/test/Transforms/JumpThreading/unreachable-loops.ll Removed: ################################################################################ diff --git a/llvm/lib/Analysis/VectorUtils.cpp b/llvm/lib/Analysis/VectorUtils.cpp index bd69055ac246..90726979ca4a 100644 --- a/llvm/lib/Analysis/VectorUtils.cpp +++ b/llvm/lib/Analysis/VectorUtils.cpp @@ -290,6 +290,10 @@ Value *llvm::findScalarElement(Value *V, unsigned EltNo) { if (EltNo == IIElt) return III->getOperand(1); + // Guard against infinite loop on malformed, unreachable IR. + if (III == III->getOperand(0)) + return nullptr; + // Otherwise, the insertelement doesn't modify the value, recurse on its // vector input. return findScalarElement(III->getOperand(0), EltNo); diff --git a/llvm/test/Transforms/JumpThreading/unreachable-loops.ll b/llvm/test/Transforms/JumpThreading/unreachable-loops.ll index 3f75aeae906c..a0f1c2127209 100644 --- a/llvm/test/Transforms/JumpThreading/unreachable-loops.ll +++ b/llvm/test/Transforms/JumpThreading/unreachable-loops.ll @@ -1,11 +1,12 @@ ; RUN: opt -jump-threading -S < %s | FileCheck %s ; RUN: opt -passes=jump-threading -S < %s | FileCheck %s + ; Check the unreachable loop won't cause infinite loop ; in jump-threading when it tries to update the predecessors' ; profile metadata from a phi node. define void @unreachable_single_bb_loop() { -; CHECK-LABEL: @unreachable_single_bb_loop() +; CHECK-LABEL: @unreachable_single_bb_loop( bb: %tmp = call i32 @a() %tmp1 = icmp eq i32 %tmp, 1 @@ -15,8 +16,8 @@ bb: bb2: ; preds = %bb2 %tmp4 = icmp ne i32 %tmp, 1 switch i1 %tmp4, label %bb2 [ - i1 0, label %bb5 - i1 1, label %bb8 + i1 0, label %bb5 + i1 1, label %bb8 ] bb5: ; preds = %bb2, %bb @@ -31,7 +32,7 @@ bb8: ; preds = %bb8, %bb7, %bb5, %b } define void @unreachable_multi_bbs_loop() { -; CHECK-LABEL: @unreachable_multi_bbs_loop() +; CHECK-LABEL: @unreachable_multi_bbs_loop( bb: %tmp = call i32 @a() %tmp1 = icmp eq i32 %tmp, 1 @@ -44,8 +45,8 @@ bb3: ; preds = %bb2 bb2: ; preds = %bb3 %tmp4 = icmp ne i32 %tmp, 1 switch i1 %tmp4, label %bb3 [ - i1 0, label %bb5 - i1 1, label %bb8 + i1 0, label %bb5 + i1 1, label %bb8 ] bb5: ; preds = %bb2, %bb @@ -60,4 +61,85 @@ bb8: ; preds = %bb8, %bb7, %bb5, %b } declare i32 @a() +; This gets into a state that could cause instruction simplify +; to hang - an insertelement instruction has itself as an operand. + +define void @PR48362() { +; CHECK-LABEL: @PR48362( +cleanup1491: ; preds = %for.body1140 + switch i32 0, label %cleanup2343.loopexit4 [ + i32 0, label %cleanup.cont1500 + i32 128, label %lbl_555.loopexit + ] + +cleanup.cont1500: ; preds = %cleanup1491 + unreachable + +lbl_555.loopexit: ; preds = %cleanup1491 + br label %for.body1509 + +for.body1509: ; preds = %for.inc2340, %lbl_555.loopexit + %l_580.sroa.0.0 = phi <4 x i32> [ <i32 1684658741, i32 1684658741, i32 1684658741, i32 1684658741>, %lbl_555.loopexit ], [ %l_580.sroa.0.2, %for.inc2340 ] + %p_55.addr.10 = phi i16 [ 0, %lbl_555.loopexit ], [ %p_55.addr.11, %for.inc2340 ] + %i82 = load i32, i32* undef, align 1 + %tobool1731.not = icmp eq i32 %i82, 0 + br i1 %tobool1731.not, label %if.end1733, label %if.then1732 + +if.then1732: ; preds = %for.body1509 + br label %cleanup2329 + +if.end1733: ; preds = %for.body1509 + %tobool1735.not = icmp eq i16 %p_55.addr.10, 0 + br i1 %tobool1735.not, label %if.then1736, label %if.else1904 + +if.then1736: ; preds = %if.end1733 + br label %cleanup2329 + +if.else1904: ; preds = %if.end1733 + br label %for.body1911 + +for.body1911: ; preds = %if.else1904 + %l_580.sroa.0.4.vec.extract683 = extractelement <4 x i32> %l_580.sroa.0.0, i32 2 + %xor2107 = xor i32 undef, %l_580.sroa.0.4.vec.extract683 + br label %land.end2173 + +land.end2173: ; preds = %for.body1911 + br i1 undef, label %if.end2178, label %cleanup2297 + +if.end2178: ; preds = %land.end2173 + %l_580.sroa.0.2.vec.insert = insertelement <4 x i32> %l_580.sroa.0.0, i32 undef, i32 1 + br label %cleanup2297 + +cleanup2297: ; preds = %if.end2178, %land.end2173 + %l_580.sroa.0.1 = phi <4 x i32> [ %l_580.sroa.0.2.vec.insert, %if.end2178 ], [ %l_580.sroa.0.0, %land.end2173 ] + br label %cleanup2329 + +cleanup2329: ; preds = %cleanup2297, %if.then1736, %if.then1732 + %l_580.sroa.0.2 = phi <4 x i32> [ %l_580.sroa.0.0, %if.then1736 ], [ %l_580.sroa.0.1, %cleanup2297 ], [ %l_580.sroa.0.0, %if.then1732 ] + %cleanup.dest.slot.11 = phi i32 [ 0, %if.then1736 ], [ undef, %cleanup2297 ], [ 129, %if.then1732 ] + %p_55.addr.11 = phi i16 [ %p_55.addr.10, %if.then1736 ], [ undef, %cleanup2297 ], [ %p_55.addr.10, %if.then1732 ] + switch i32 %cleanup.dest.slot.11, label %cleanup2343.loopexit [ + i32 0, label %cleanup.cont2339 + i32 129, label %crit_edge114 + ] + +cleanup.cont2339: ; preds = %cleanup2329 + br label %for.inc2340 + +for.inc2340: ; preds = %cleanup.cont2339 + br i1 undef, label %for.body1509, label %crit_edge115 + +crit_edge114: ; preds = %cleanup2329 + unreachable + +crit_edge115: ; preds = %for.inc2340 + unreachable + +cleanup2343.loopexit: ; preds = %cleanup2329 + unreachable + +cleanup2343.loopexit4: ; preds = %cleanup1491 + unreachable +} + !0 = !{!"branch_weights", i32 2146410443, i32 1073205} _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits