From f8ab3ef1eb83f2fdbe54924ba8a46646e3421193 Mon Sep 17 00:00:00 2001 From: Michael Kuperstein Date: Wed, 6 Jan 2016 18:40:11 +0000 Subject: [PATCH] [ShrinkWrap] Fix FindIDom to only have one kind of failure. FindIDom() can fail in two different ways - it can either return nullptr or the block itself, depending on the circumstances. Some users of FindIDom() check one error condition, while others check the other. Change it to always return nullptr on failure. This fixes PR26004. Differential Revision: http://reviews.llvm.org/D15847 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256955 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/ShrinkWrap.cpp | 10 ++++----- test/CodeGen/X86/shrinkwrap-hang.ll | 32 +++++++++++++++++++++++++++++ 2 files changed, 36 insertions(+), 6 deletions(-) create mode 100644 test/CodeGen/X86/shrinkwrap-hang.ll diff --git a/lib/CodeGen/ShrinkWrap.cpp b/lib/CodeGen/ShrinkWrap.cpp index f8aa1e2b0b9..2ff86aaa51c 100644 --- a/lib/CodeGen/ShrinkWrap.cpp +++ b/lib/CodeGen/ShrinkWrap.cpp @@ -263,6 +263,8 @@ MachineBasicBlock *FindIDom(MachineBasicBlock &Block, ListOfBBs BBs, if (!IDom) break; } + if (IDom == &Block) + return nullptr; return IDom; } @@ -352,13 +354,9 @@ void ShrinkWrap::updateSaveRestorePoints(MachineBasicBlock &MBB, if (MLI->getLoopDepth(Save) > MLI->getLoopDepth(Restore)) { // Push Save outside of this loop if immediate dominator is different // from save block. If immediate dominator is not different, bail out. - MachineBasicBlock *IDom = FindIDom<>(*Save, Save->predecessors(), *MDT); - if (IDom != Save) - Save = IDom; - else { - Save = nullptr; + Save = FindIDom<>(*Save, Save->predecessors(), *MDT); + if (!Save) break; - } } else { // If the loop does not exit, there is no point in looking // for a post-dominator outside the loop. diff --git a/test/CodeGen/X86/shrinkwrap-hang.ll b/test/CodeGen/X86/shrinkwrap-hang.ll new file mode 100644 index 00000000000..e1e4eefb3ef --- /dev/null +++ b/test/CodeGen/X86/shrinkwrap-hang.ll @@ -0,0 +1,32 @@ +; RUN: llc %s -o - -enable-shrink-wrap=true | FileCheck %s + +target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128" +target triple = "i686-pc-linux" + +@b = global i32 1, align 4 +@a = common global i32 0, align 4 + +declare void @fn1() #0 + +; CHECK-LABEL: fn2: +define void @fn2() #0 { +entry: + %0 = load i32, i32* @b, align 4 + %tobool = icmp eq i32 %0, 0 + br i1 %tobool, label %if.end, label %lbl + +lbl: ; preds = %if.end, %entry + store i32 0, i32* @b, align 4 + br label %if.end + +if.end: ; preds = %entry, %lbl + tail call void @fn1() + %1 = load i32, i32* @b, align 4 + %tobool1 = icmp eq i32 %1, 0 + br i1 %tobool1, label %if.end3, label %lbl + +if.end3: ; preds = %if.end + ret void +} + +attributes #0 = { norecurse nounwind "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="pentium4" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" } -- 2.34.1