https://llvm.org/bugs/show_bug.cgi?id=30371
Bug ID: 30371 Summary: [x86, AVX] poor codegen for shufflevector with constants Product: libraries Version: trunk Hardware: PC OS: All Status: NEW Severity: normal Priority: P Component: Backend: X86 Assignee: unassignedb...@nondot.org Reporter: spatel+l...@rotateright.com CC: llvm-bugs@lists.llvm.org Classification: Unclassified Testing with llc built from r281342: define <4 x float> @does_it_blend(float %f) { %a0 = insertelement <4 x float> undef, float %f, i32 0 %ret = shufflevector <4 x float> %a0, <4 x float> <float undef, float 4.0, float 5.0, float 3.0>, <4 x i32> <i32 4, i32 5, i32 6, i32 7> ret <4 x float> %ret } This should be a blendps or insertps with a vector constant, but we scalarized the constant loads, so what could have been 2 ops (load+blend) became 6 ops: $ ./llc blender.ll -o - -mattr=avx vinsertps $16, LCPI0_0(%rip), %xmm0, %xmm0 ## xmm0 = xmm0[0],mem[0],xmm0[2,3] vinsertps $32, LCPI0_1(%rip), %xmm0, %xmm0 ## xmm0 = xmm0[0,1],mem[0],xmm0[3] vinsertps $48, LCPI0_2(%rip), %xmm0, %xmm0 ## xmm0 = xmm0[0,1,2],mem[0] retq -- You are receiving this mail because: You are on the CC list for the bug.
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