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Merging r231563 from adibiagio: [DAGCombiner] Fix wrong folding of AND dag nodes. This patch fixes the logic in the DAGCombiner that folds an AND node according to rule: (and (X (load V)), C) -> (X (load V)) An AND between a vector load 'X' and a constant build_vector 'C' can be folded into the load itself only if we can prove that the AND operation is redundant. The algorithm implemented by 'visitAND' firstly computes the splat value 'S' from C, and then checks if S has the lower 'B' bits set (where B is the size in bits of the vector element type). The algorithm takes into account also the 'undef' bits in the splat mask. Unfortunately, the algorithm only worked under the assumption that the size of S is a multiple of the vector element type. With this patch, we conservatively avoid folding the AND if the splat bits are not compatible with the vector element type. Added X86 test and-load-fold.ll Differential Revision: http://reviews.llvm.org/D8085 git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_36@231702 91177308-0d34-0410-b5e6-96231b3b80d8 Joerg Sonnenberger 5 years ago
2 changed file(s) with 22 addition(s) and 3 deletion(s). Raw diff Collapse all Expand all
27872787 SplatBitSize = SplatBitSize * 2)
27882788 SplatValue |= SplatValue.shl(SplatBitSize);
27892789
2790 Constant = APInt::getAllOnesValue(BitWidth);
2791 for (unsigned i = 0, n = SplatBitSize/BitWidth; i < n; ++i)
2792 Constant &= SplatValue.lshr(i*BitWidth).zextOrTrunc(BitWidth);
2790 // Make sure that variable 'Constant' is only set if 'SplatBitSize' is a
2791 // multiple of 'BitWidth'. Otherwise, we could propagate a wrong value.
2792 if (SplatBitSize % BitWidth == 0) {
2793 Constant = APInt::getAllOnesValue(BitWidth);
2794 for (unsigned i = 0, n = SplatBitSize/BitWidth; i < n; ++i)
2795 Constant &= SplatValue.lshr(i*BitWidth).zextOrTrunc(BitWidth);
2796 }
27932797 }
27942798 }
27952799
0 ; RUN: llc -mtriple=x86_64-unknown-unknown -mcpu=generic < %s | FileCheck %s
1
2 ; Verify that the DAGCombiner doesn't wrongly remove the 'and' from the dag.
3
4 define i8 @foo(<4 x i8>* %V) {
5 ; CHECK-LABEL: foo:
6 ; CHECK: pand
7 ; CHECK: ret
8 entry:
9 %Vp = bitcast <4 x i8>* %V to <3 x i8>*
10 %V3i8 = load <3 x i8>* %Vp, align 4
11 %0 = and <3 x i8> %V3i8,
12 %1 = extractelement <3 x i8> %0, i64 2
13 ret i8 %1
14 }