On 12/3/2021 2:21 AM, Alexandre Oliva via Gcc-patches wrote:
When -fif-conversion2 is enabled, we attempt to replace conditional
branches around unconditional traps with conditional traps. That
canonicalizes compares, which may change an immediate that barely fits
into one that doesn't.
The compare for the trap is first checked using the predicates of
cbranch predicates, and then, compare and conditional trap insns are
emitted and recognized.
In the failing s390x testcase, i <=u 0xffff_ffff is canonicalized into
i <u 0x1_0000_0000, and the latter immediate doesn't fit. The insn
predicates (both cbranch and cmpdi_ccu) happily accept it, since the
register allocator has no trouble getting them into registers. The
problem is that ifcvt2 runs after reload, so we recognize the compare
insn successfully, but later on we barf when we find that none of the
constraints fit.
This patch arranges for the trap_if-issuing bits in ifcvt to validate
post-reload insns using a stricter test that also checks that operands
fit the constraints.
Regstrapped on x86_64-linux-gnu. Also verified that the testcase passes
on a cross to s390x-linux-gnu. Ok to install?
for gcc/ChangeLog
PR rtl-optimization/103028
* ifcvt.c (find_cond_trap): Validate new insns more strictly
after reload.
for gcc/testsuite/ChangeLog
PR rtl-optimization/103028
* gcc.dg/pr103028.c: New.
OK. I wouldn't be surprised if there's other cases were we're using
recog_memoized post-reload when we should be using valid_insn_p.
Jeff
