https://bugs.llvm.org/show_bug.cgi?id=36191
Bug ID: 36191
Summary: [X86][AVX512] Failure to fold broadcast into 'zmm'
instruction for fake xmm/ymm (NoVLX) instructions
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: llvm-...@redking.me.uk
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
zvi.racko...@intel.com
define <4 x i64> @mul_19(<4 x i64>) {
%2 = mul <4 x i64> %0, <i64 19, i64 19, i64 19, i64 19>
ret <4 x i64> %2
}
Without AVX512VL, we cheat and perform many AVX512 xmm/ymm instructions on the
ZMM register. Unfortunately we fail to fold broadcast loads into these,
increasing register pressure:
llc -mattr=+avx512dq,+avx512vl
.LCPI0_0:
.quad 19 # 0x13
_Z6mul_19Dv4_x: # @_Z6mul_19Dv4_x
vpmullq .LCPI0_0(%rip){1to4}, %ymm0, %ymm0
retq
llc -mattr=+avx512dq
.LCPI0_0:
.quad 19 # 0x13
_Z6mul_19Dv4_x: # @_Z6mul_19Dv4_x
vpbroadcastq .LCPI0_0(%rip), %ymm1 # ymm1 = [19,19,19,19]
vpmullq %zmm1, %zmm0, %zmm0
retq
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