From 1a3f524e3c4da0393569f007ece81fe3ecb9352d Mon Sep 17 00:00:00 2001
From: Guozhi Wei <carrot@google.com>
Date: Thu, 15 Mar 2018 17:49:12 +0000
Subject: [PATCH] [PPC] Avoid non-simple MVT in STBRX optimization

PR35402 triggered this case. It bswap and stores a 48bit value, current STBRX optimization transforms it into STBRX. Unfortunately 48bit is not a simple MVT, there is no PPC instruction to support it, and it can't be automatically expanded by llvm, so caused a crash.

This patch detects the non-simple MVT and returns early.

Differential Revision: https://reviews.llvm.org/D44500

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@327651 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/PowerPC/PPCISelLowering.cpp |  6 +++++-
 test/CodeGen/PowerPC/pr35402.ll        | 18 ++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/PowerPC/pr35402.ll

diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index f9de65f..eeb1bf1 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -12221,6 +12221,11 @@ SDValue PPCTargetLowering::PerformDAGCombine(SDNode *N,
          N->getOperand(1).getValueType() == MVT::i16 ||
          (Subtarget.hasLDBRX() && Subtarget.isPPC64() &&
           N->getOperand(1).getValueType() == MVT::i64))) {
+      // STBRX can only handle simple types.
+      EVT mVT = cast<StoreSDNode>(N)->getMemoryVT();
+      if (mVT.isExtended())
+        break;
+
       SDValue BSwapOp = N->getOperand(1).getOperand(0);
       // Do an any-extend to 32-bits if this is a half-word input.
       if (BSwapOp.getValueType() == MVT::i16)
@@ -12228,7 +12233,6 @@ SDValue PPCTargetLowering::PerformDAGCombine(SDNode *N,
 
       // If the type of BSWAP operand is wider than stored memory width
       // it need to be shifted to the right side before STBRX.
-      EVT mVT = cast<StoreSDNode>(N)->getMemoryVT();
       if (Op1VT.bitsGT(mVT)) {
         int Shift = Op1VT.getSizeInBits() - mVT.getSizeInBits();
         BSwapOp = DAG.getNode(ISD::SRL, dl, Op1VT, BSwapOp,
diff --git a/test/CodeGen/PowerPC/pr35402.ll b/test/CodeGen/PowerPC/pr35402.ll
new file mode 100644
index 0000000..06e6d96
--- /dev/null
+++ b/test/CodeGen/PowerPC/pr35402.ll
@@ -0,0 +1,18 @@
+; RUN: llc -O2 < %s | FileCheck %s
+target triple = "powerpc64le-linux-gnu"
+
+define void @test(i8* %p, i64 %data) {
+entry:
+  %0 = tail call i64 @llvm.bswap.i64(i64 %data)
+  %ptr = bitcast i8* %p to i48*
+  %val = trunc i64 %0 to i48
+  store i48 %val, i48* %ptr, align 1
+  ret void
+
+; CHECK:     sth
+; CHECK:     stw
+; CHECK-NOT: stdbrx
+
+}
+
+declare i64 @llvm.bswap.i64(i64)
-- 
1.8.3.1