[llvm] r204623 - [X86] Fix non-determinism in LowerVectorAllZeroTest

[Adam Nemet]

Author: anemet
Date: Mon Mar 24 11:52:08 2014
New Revision: 204623

URL: http://llvm.org/viewvc/llvm-project?rev=204623&view=rev
Log:
[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>

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=204623&r1=204622&r2=204623&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Mon Mar 24 11:52:08 2014
@@ -9454,6 +9454,7 @@ static SDValue LowerVectorAllZeroTest(SD
 
   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(SD
           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(SD
          "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;