From 813b365fd0cc3b916f02fc58f343dc404674a12d Mon Sep 17 00:00:00 2001 From: Krzysztof Parzyszek <kparzysz@codeaurora.org> Date: Wed, 21 Oct 2015 02:40:06 +0000 Subject: [PATCH] Tail duplication can mix incompatible registers in phi nodes Do not tail duplicate blocks where the successor has a phi node, and the corresponding value in that phi node uses a subregister. http://reviews.llvm.org/D13922 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@250877 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/TailDuplication.cpp | 21 ++++++++++++++ test/CodeGen/Hexagon/tail-dup-subreg-abort.ll | 28 +++++++++++++++++++ 2 files changed, 49 insertions(+) create mode 100644 test/CodeGen/Hexagon/tail-dup-subreg-abort.ll diff --git a/lib/CodeGen/TailDuplication.cpp b/lib/CodeGen/TailDuplication.cpp index c2e8b937374..ff86dabfac5 100644 --- a/lib/CodeGen/TailDuplication.cpp +++ b/lib/CodeGen/TailDuplication.cpp @@ -607,6 +607,27 @@ TailDuplicatePass::shouldTailDuplicate(const MachineFunction &MF, return false; } + // Check if any of the successors of TailBB has a PHI node in which the + // value corresponding to TailBB uses a subregister. + // If a phi node uses a register paired with a subregister, the actual + // "value type" of the phi may differ from the type of the register without + // any subregisters. Due to a bug, tail duplication may add a new operand + // without a necessary subregister, producing an invalid code. This is + // demonstrated by test/CodeGen/Hexagon/tail-dup-subreg-abort.ll. + // Disable tail duplication for this case for now, until the problem is + // fixed. + for (auto SB : TailBB.successors()) { + for (auto &I : *SB) { + if (!I.isPHI()) + break; + unsigned Idx = getPHISrcRegOpIdx(&I, &TailBB); + assert(Idx != 0); + MachineOperand &PU = I.getOperand(Idx); + if (PU.getSubReg() != 0) + return false; + } + } + if (HasIndirectbr && PreRegAlloc) return true; diff --git a/test/CodeGen/Hexagon/tail-dup-subreg-abort.ll b/test/CodeGen/Hexagon/tail-dup-subreg-abort.ll new file mode 100644 index 00000000000..82dae2cc586 --- /dev/null +++ b/test/CodeGen/Hexagon/tail-dup-subreg-abort.ll @@ -0,0 +1,28 @@ +; RUN: llc -march=hexagon -O2 -disable-cgp < %s +; REQUIRES: asserts +; +; Tail duplication can ignore subregister information on PHI nodes, and as +; a result, generate COPY instructions between registers of different classes. +; This could lead to HexagonInstrInfo::copyPhysReg aborting on an unhandled +; src/dst combination. +; +define i32 @foo(i32 %x, i64 %y) nounwind { +entry: + %a = icmp slt i32 %x, 0 + %lo = trunc i64 %y to i32 + br i1 %a, label %next, label %tail +tail: + br label %join +next: + %c = icmp eq i32 %x, 0 + br i1 %c, label %b1, label %tail +b1: + %t1 = lshr i64 %y, 32 + %hi = trunc i64 %t1 to i32 + br label %join +join: + %val = phi i32 [ %hi, %b1 ], [ %lo, %tail ] + ret i32 %val +} + +