fallback: legalize: G_LSHR <2 x s64>

Run:	main-04ca53e65f-20261014-105623
Kind:	fallback
Category:	legalize: G_LSHR <2 x s64>
Occurrences:	26 in 13 configs, 4 test files
Snippet from:	rvp-simd-64.ll @test_pasubu_w via llvm-extract
Config:	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
Local check:	reproduces at 04ca53e65f
Compiler Explorer:	not uploaded (over --godbolt-limit or disabled)

Snippet:

define <2 x i32> @test_pasubu_w(<2 x i32> %a, <2 x i32> %b) {
  %a_ext = zext <2 x i32> %a to <2 x i64>
  %b_ext = zext <2 x i32> %b to <2 x i64>
  %sub = sub <2 x i64> %a_ext, %b_ext
  %res = lshr <2 x i64> %sub, splat (i64 1)
  %res_trunc = trunc <2 x i64> %res to <2 x i32>
  ret <2 x i32> %res_trunc
}

Reproduce:

llc -mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %7:_(<2 x s64>) = G_LSHR %4:_, %5:_(<2 x s64>) (in function: test_pasubu_w)
warning: Instruction selection used fallback path for test_pasubu_w

Occurrences (26):

Input	Function	Config
rvp-simd-64.ll	test_pasubu_w	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pmulh_w	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pmulhu_w	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pmulhsu_w	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pmulhsu_w_commuted	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pmulhr_w	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pmulhru_w	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pmulhrsu_w	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pmulhrsu_w_commuted	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pmulhu_v2i32	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
umulh.ll	umulh_v2i32	`-mtriple=riscv32 -mattr=+m`
umulh.ll	umulh_v2i32	`-mtriple=riscv64 -mattr=+m`
frameaddr-returnaddr.766e6201b8.ll (mutant of frameaddr-returnaddr.ll)	test_frameaddress_3_alloca	`-mtriple=riscv32 -verify-machineinstrs`
frameaddr-returnaddr.ccda1fcb3d.ll (mutant of frameaddr-returnaddr.ll)	test_frameaddress_3_alloca	`-mtriple=riscv64 -verify-machineinstrs`
inline-asm-mem-constraint.081fe1ba9f.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv64 -code-model=medium -verify-machineinstrs`
inline-asm-mem-constraint.0de94c51a9.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv32 -verify-machineinstrs`
inline-asm-mem-constraint.3c540e5487.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv64 -code-model=medium -verify-machineinstrs -no-integrated-as`
inline-asm-mem-constraint.4451d9464b.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv32 -verify-machineinstrs -no-integrated-as`
inline-asm-mem-constraint.5db9c28aca.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv64 -code-model=large -verify-machineinstrs`
inline-asm-mem-constraint.5f0801920e.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv32 -code-model=medium -verify-machineinstrs`
inline-asm-mem-constraint.6a3188f97c.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv32 -code-model=medium -verify-machineinstrs -no-integrated-as`
inline-asm-mem-constraint.b9a8eba9cc.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv64 -verify-machineinstrs`
inline-asm-mem-constraint.d7987742bc.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv64 -verify-machineinstrs -no-integrated-as`
inline-asm-mem-constraint.f1e1da8412.ll (mutant of inline-asm-mem-constraint.ll)	constraint_A_with_global_3	`-mtriple=riscv64 -code-model=large -verify-machineinstrs -no-integrated-as`
umulh.48817cdde7.ll (mutant of umulh.ll)	umulh_v2i32	`-mtriple=riscv32 -mattr=+m`
umulh.bd6efb007a.ll (mutant of umulh.ll)	umulh_v2i32	`-mtriple=riscv64 -mattr=+m`

Generated 2026-10-15 08:05 UTC.