fallback: legalize: G_BITCAST s64,<2 x s32>

Run:	explore-bc8218b282-20261015-075519
Kind:	fallback
Category:	legalize: G_BITCAST s64,<2 x s32>
Occurrences:	19 in 7 configs, 4 test files
Snippet from:	mul.ll @mul_add_bitcast via llvm-extract
Config:	`-mtriple=riscv32 -mattr=+m -verify-machineinstrs`
Local check:	reproduces at bc8218b282
Compiler Explorer:	not uploaded (over --godbolt-limit or disabled)

Snippet:

define i64 @mul_add_bitcast(i64 %x) {
  %add = add i64 %x, 1
  %bitcast = bitcast <2 x i32> zeroinitializer to i64
  %mul = mul i64 %add, %bitcast
  ret i64 %mul
}

Reproduce:

llc -mtriple=riscv32 -mattr=+m -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv32 -mattr=+m -verify-machineinstrs -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %7:_(s64) = G_BITCAST %5:_(<2 x s32>) (in function: mul_add_bitcast)
warning: Instruction selection used fallback path for mul_add_bitcast

Occurrences (19):

Input	Function	Config
mul.ll	mul_add_bitcast	`-mtriple=riscv32 -mattr=+m -verify-machineinstrs`
mul.ll	mul_add_bitcast	`-mtriple=riscv32 -verify-machineinstrs`
mul.ll	mul_add_bitcast	`-mtriple=riscv64 -mattr=+m -verify-machineinstrs`
mul.ll	mul_add_bitcast	`-mtriple=riscv64 -verify-machineinstrs`
rvp-bitcast-const-fold.ll	pnot_v2i32	`-mtriple=riscv32 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-bitcast-const-fold.ll	pnot_v2i32	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-bitcast-paired.ll	add_v2i32_via_bitcast	`-mtriple=riscv32 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-bitcast-paired.ll	add_v2i32_via_bitcast	`-mtriple=riscv32 -mattr=+experimental-p,+m,+zbb,+d -verify-machineinstrs`
rvp-bitcast-paired.ll	add_v2i32_via_bitcast	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pnclipp_v2i32	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pnclipup_v2i32	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-bitcast-const-fold.1df66a721d.ll (mutant of rvp-bitcast-const-fold.ll)	pnot_v2i32	`-mtriple=riscv32 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-bitcast-const-fold.a52229c7de.ll (mutant of rvp-bitcast-const-fold.ll)	pnot_v2i32	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-bitcast-paired.2a65d909f7.ll (mutant of rvp-bitcast-paired.ll)	add_v2i32_via_bitcast	`-mtriple=riscv32 -mattr=+experimental-p,+m,+zbb,+d -verify-machineinstrs`
rvp-bitcast-paired.39daad0cc9.ll (mutant of rvp-bitcast-paired.ll)	add_v2i32_via_bitcast	`-mtriple=riscv32 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-bitcast-paired.989d9bdc69.ll (mutant of rvp-bitcast-paired.ll)	add_v2i32_via_bitcast	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-bitcast-paired.c0275bddbc.ll (mutant of rvp-bitcast-paired.ll)	add_v2i32_via_bitcast	`-mtriple=riscv32 -mattr=+experimental-p,+m,+zbb,+d -verify-machineinstrs`
rvp-bitcast-paired.fe31b6797e.ll (mutant of rvp-bitcast-paired.ll)	add_v2i32_via_bitcast	`-mtriple=riscv32 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-bitcast-paired.fe55efc650.ll (mutant of rvp-bitcast-paired.ll)	add_v2i32_via_bitcast	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`

Generated 2026-10-15 08:05 UTC.