tree f6f02ddd5ad0a273dd17377c58d4e8443c7c1a17
parent 517f7e3f02b4c945d2b4bdabb490961cf986391e
author Vineet Gupta <vineetg@rivosinc.com> 1744734548 -0700
committer Vineet Gupta <vineetg@rivosinc.com> 1744734548 -0700

RISC-V: vsetvl: elide abnormal edges from LCM computations [PR119533]

vsetvl phase4 uses LCM guided info to insert VSETVL insns, including a
straggler loop for "mising vsetvls" on certain edges. Currently it
asserts on encountering EDGE_ABNORMAL.

When enabling go frontend with V enabled, libgo build hits the assert.

The solution is to prevent abnormal edges from getting into LCM at all
(my prior attempt at this just ignored them after LCM which is not
right). Existing invalid_opt_bb_p () current does this for BB predecessors
but not for successors which is what the patch adds.

Crucially, the ICE/fix also depends on avoiding vsetvl hoisting past
non-transparent blocks: That is taken care of by Robin's patch
"RISC-V: Do not lift up vsetvl into non-transparent blocks [PR119547]"
for a different yet related issue.

Reported-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>

	PR target/119533

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (invalid_opt_bb_p): Check for
	EDGE_ABNOMAL.
	(pre_vsetvl::compute_lcm_local_properties): Initialize kill
	bitmap.
	Debug dump skipped edge.

gcc/testsuite/ChangeLog:

	* go.dg/pr119533-riscv.go: New test.
	* go.dg/pr119533-riscv-2.go: New test.