From: Adam Nemet <anemet@apple.com>
Date: Mon, 24 Mar 2014 16:52:08 +0000 (+0000)
Subject: [X86] Fix non-determinism in LowerVectorAllZeroTest
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=a1b54dd1ffff68195ecfe106dceeb73e351dd6c9;p=oota-llvm.git

[X86] Fix non-determinism in LowerVectorAllZeroTest

This can be observed with the old testcase of CodeGen/X86/pr12312.ll:

47c47
<       vorps   %ymm0, %ymm1, %ymm0
---
>       vorps   %ymm1, %ymm0, %ymm0
97c97
<       vorps   %ymm1, %ymm0, %ymm0
---
>       vorps   %ymm0, %ymm1, %ymm0

The vector VecIns is populated with all the values from VecInMap. This is done
while iterating VecInMap.  VecInMap uses a hash of pointer values so the
resulting order can vary depending on the memory layout.

The fix is to populate the vector VecIns earlier as VecInMap is populated.
This is done in DAG traversal order.

Fixes <rdar://problem/16398806>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204623 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index bb501aa44be..8fbfb8497fd 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -9454,6 +9454,7 @@ static SDValue LowerVectorAllZeroTest(SDValue Op, const X86Subtarget *Subtarget,
 
   SmallVector<SDValue, 8> Opnds;
   DenseMap<SDValue, unsigned> VecInMap;
+  SmallVector<SDValue, 8> VecIns;
   EVT VT = MVT::Other;
 
   // Recognize a special case where a vector is casted into wide integer to
@@ -9493,6 +9494,7 @@ static SDValue LowerVectorAllZeroTest(SDValue Op, const X86Subtarget *Subtarget,
           VT != VecInMap.begin()->first.getValueType())
         return SDValue();
       M = VecInMap.insert(std::make_pair(ExtractedFromVec, 0)).first;
+      VecIns.push_back(ExtractedFromVec);
     }
     M->second |= 1U << cast<ConstantSDNode>(Idx)->getZExtValue();
   }
@@ -9501,14 +9503,12 @@ static SDValue LowerVectorAllZeroTest(SDValue Op, const X86Subtarget *Subtarget,
          "Not extracted from 128-/256-bit vector.");
 
   unsigned FullMask = (1U << VT.getVectorNumElements()) - 1U;
-  SmallVector<SDValue, 8> VecIns;
 
   for (DenseMap<SDValue, unsigned>::const_iterator
         I = VecInMap.begin(), E = VecInMap.end(); I != E; ++I) {
     // Quit if not all elements are used.
     if (I->second != FullMask)
       return SDValue();
-    VecIns.push_back(I->first);
   }
 
   EVT TestVT = VT.is128BitVector() ? MVT::v2i64 : MVT::v4i64;