https://bugs.llvm.org/show_bug.cgi?id=51281
Bug ID: 51281
Summary: [X86][AVX] Incorrect decoding of constant vector data
from X86ISD::SUBV_BROADCAST_LOAD nodes
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: llvm-...@redking.me.uk
Reporter: llvm-...@redking.me.uk
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
llvm-...@redking.me.uk, pengfei.w...@intel.com,
spatel+l...@rotateright.com
Internal fuzz tests have found an issue that appeared after rGc8472db0a88701.
The more aggressive creation of X86ISD::SUBV_BROADCAST_LOAD nodes has exposed
an existing bug with incorrect constant decoding in
getTargetConstantBitsFromNode if its referencing a constant pool entry larger
than the subvector size.
define <16 x float> @shuffc(<8 x float> %a0) {
%shuffle = shufflevector <8 x float> %a0, <8 x float> <float poison, float
0x3FD6BB78C0000000, float poison, float poison, float poison, float poison,
float 0.000000e+00, float poison>, <16 x i32> <i32 7, i32 7, i32 1, i32 1, i32
6, i32 3, i32 6, i32 0, i32 14, i32 0, i32 9, i32 9, i32 7, i32 1, i32 5, i32
9>
ret <16 x float> %shuffle
}
https://c.godbolt.org/z/b9W3xKe1e
codegen (same for trunk and 12.x):
shuffc: # @shuffc
vextractf128 xmm1, ymm0, 1
vperm2f128 ymm3, ymm0, ymm0, 1 # ymm3 = ymm0[2,3,0,1]
vshufps xmm2, xmm0, xmm1, 49 # xmm2 = xmm0[1,0],xmm1[3,0]
vshufps xmm1, xmm2, xmm1, 210 # xmm1 = xmm2[2,0],xmm1[1,3]
vmovsldup xmm2, xmm0 # xmm2 = xmm0[0,0,2,2]
vblendps ymm0, ymm3, ymm0, 66 # ymm0 =
ymm3[0],ymm0[1],ymm3[2,3,4,5],ymm0[6],ymm3[7]
vpermilps ymm0, ymm0, ymmword ptr [rip + .LCPI0_1] # ymm0 =
ymm0[3,3,1,1,6,7,6,4]
vinsertf128 ymm1, ymm2, xmm1, 1
vblendps ymm1, ymm1, ymmword ptr [rip + .LCPI0_0], 141 # ymm1 =
mem[0],ymm1[1],mem[2,3],ymm1[4,5,6],mem[7]
ret
trunk constant table:
.LCPI0_0:
.long 0x00000000 # float 0
.zero 4
.long 0x3eb5dbc6 # float 0.355192363
.long 0x3eb5dbc6 # float 0.355192363
.zero 4
.long 0x3eb5dbc6 # float 0.355192363
.zero 4
.zero 4
12.x constant table:
.LCPI0_0:
.long 0x00000000 # float 0
.zero 4
.long 0x3eb5dbc6 # float 0.355192363
.long 0x3eb5dbc6 # float 0.355192363
.zero 4
.long 0x3eb5dbc6 # float 0.355192363
.long 0x3eb5dbc6 # float 0.355192363
.long 0x3eb5dbc6 # float 0.355192363
I'm currently working on a patch.
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