[llvm] r296352 - [X86] Use APInt instead of SmallBitVector for tracking undef elements in constant pool shuffle decoding

[Craig Topper via llvm-commits]

Author: ctopper
Date: Mon Feb 27 10:15:25 2017
New Revision: 296352

URL: http://llvm.org/viewvc/llvm-project?rev=296352&view=rev
Log:
[X86] Use APInt instead of SmallBitVector for tracking undef elements in constant pool shuffle decoding

Summary:
SmallBitVector uses a malloc for more than 58 bits on a 64-bit target and more than 27 bits on a 32-bit target. Some of the vector types we deal with here use more than those number of elements and therefore cause a malloc.

APInt on the other hand supports up to 64 bits without a malloc. That's the maximum number of bits we need here so we can avoid a malloc for all cases by using APInt. This will incur a minor increase in stack usage due to APInt storing the bit count separately from the data bits unlike SmallBitVector, but that should be ok.

Reviewers: RKSimon

Reviewed By: RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D30386

Modified:
    llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp

Modified: llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp?rev=296352&r1=296351&r2=296352&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ShuffleDecodeConstantPool.cpp Mon Feb 27 10:15:25 2017
@@ -14,7 +14,7 @@
 
 #include "X86ShuffleDecodeConstantPool.h"
 #include "Utils/X86ShuffleDecode.h"
-#include "llvm/ADT/SmallBitVector.h"
+#include "llvm/ADT/APInt.h"
 #include "llvm/CodeGen/MachineValueType.h"
 #include "llvm/IR/Constants.h"
 
@@ -25,7 +25,7 @@
 namespace llvm {
 
 static bool extractConstantMask(const Constant *C, unsigned MaskEltSizeInBits,
-                                SmallBitVector &UndefElts,
+                                APInt &UndefElts,
                                 SmallVectorImpl<uint64_t> &RawMask) {
   // It is not an error for shuffle masks to not be a vector of
   // MaskEltSizeInBits because the constant pool uniques constants by their
@@ -73,7 +73,7 @@ static bool extractConstantMask(const Co
          "Unaligned shuffle mask size");
 
   unsigned NumMaskElts = CstSizeInBits / MaskEltSizeInBits;
-  UndefElts = SmallBitVector(NumMaskElts, false);
+  UndefElts = APInt(NumMaskElts, 0);
   RawMask.resize(NumMaskElts, 0);
 
   for (unsigned i = 0; i != NumMaskElts; ++i) {
@@ -83,7 +83,7 @@ static bool extractConstantMask(const Co
     // Only treat the element as UNDEF if all bits are UNDEF, otherwise
     // treat it as zero.
     if (EltUndef.isAllOnesValue()) {
-      UndefElts[i] = true;
+      UndefElts.setBit(i);
       RawMask[i] = 0;
       continue;
     }
@@ -103,7 +103,7 @@ void DecodePSHUFBMask(const Constant *C,
          "Unexpected vector size.");
 
   // The shuffle mask requires a byte vector.
-  SmallBitVector UndefElts;
+  APInt UndefElts;
   SmallVector<uint64_t, 32> RawMask;
   if (!extractConstantMask(C, 8, UndefElts, RawMask))
     return;
@@ -144,7 +144,7 @@ void DecodeVPERMILPMask(const Constant *
   assert((ElSize == 32 || ElSize == 64) && "Unexpected vector element size.");
 
   // The shuffle mask requires elements the same size as the target.
-  SmallBitVector UndefElts;
+  APInt UndefElts;
   SmallVector<uint64_t, 8> RawMask;
   if (!extractConstantMask(C, ElSize, UndefElts, RawMask))
     return;
@@ -179,7 +179,7 @@ void DecodeVPERMIL2PMask(const Constant
   assert((MaskTySize == 128 || MaskTySize == 256) && "Unexpected vector size.");
 
   // The shuffle mask requires elements the same size as the target.
-  SmallBitVector UndefElts;
+  APInt UndefElts;
   SmallVector<uint64_t, 8> RawMask;
   if (!extractConstantMask(C, ElSize, UndefElts, RawMask))
     return;
@@ -230,7 +230,7 @@ void DecodeVPPERMMask(const Constant *C,
          "Unexpected vector size.");
 
   // The shuffle mask requires a byte vector.
-  SmallBitVector UndefElts;
+  APInt UndefElts;
   SmallVector<uint64_t, 32> RawMask;
   if (!extractConstantMask(C, 8, UndefElts, RawMask))
     return;
@@ -285,7 +285,7 @@ void DecodeVPERMVMask(const Constant *C,
          "Unexpected vector element size.");
 
   // The shuffle mask requires elements the same size as the target.
-  SmallBitVector UndefElts;
+  APInt UndefElts;
   SmallVector<uint64_t, 8> RawMask;
   if (!extractConstantMask(C, ElSize, UndefElts, RawMask))
     return;
@@ -313,7 +313,7 @@ void DecodeVPERMV3Mask(const Constant *C
          "Unexpected vector element size.");
 
   // The shuffle mask requires elements the same size as the target.
-  SmallBitVector UndefElts;
+  APInt UndefElts;
   SmallVector<uint64_t, 8> RawMask;
   if (!extractConstantMask(C, ElSize, UndefElts, RawMask))
     return;