From 7e544ad81a55941cda38d9195e79dace243f48d0 Mon Sep 17 00:00:00 2001 From: Richard Earnshaw Date: Wed, 15 May 2024 16:06:28 +0100 Subject: arm: remove incorrect handling of FP bignums in move_or_literal_pool This hunk of code in move_or_literal_pool just looks wrong, but I can't find a testcase that will tickle it to prove it. It looks a bit like it was intended to catch cases where a bignum contained a floating-point value, but there were a number of problems with it. - It tested X_add_number == -1, but an FP bignum is indicated by any value <= 0. - It converted the floating-point value to extended precision, but that's not used on Arm beyond the legacy FPA code. No attempt was made to match the FP value to the intended memory/mov operation. Since I can't construct a viable testcase, I've just removed the existing code and made the function error out in this case: this seems more sensible than generating wrong code or trying to write something more complex that can't be tested anyway. --- gas/config/tc-arm.c | 30 ++++++++++++++++++++++++------ 1 file changed, 24 insertions(+), 6 deletions(-) (limited to 'gas/config') diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c index 343b2e7..41bcfb8 100644 --- a/gas/config/tc-arm.c +++ b/gas/config/tc-arm.c @@ -8922,14 +8922,32 @@ move_or_literal_pool (int i, enum lit_type t, bool mode_3) uint64_t v; if (inst.relocs[0].exp.X_op == O_big) { - LITTLENUM_TYPE w[X_PRECISION]; - LITTLENUM_TYPE * l; + LITTLENUM_TYPE *l; - if (inst.relocs[0].exp.X_add_number == -1) + if (inst.relocs[0].exp.X_add_number <= 0) /* FP value. */ { - gen_to_words (w, X_PRECISION, E_PRECISION); - l = w; - /* FIXME: Should we check words w[2..5] ? */ + /* FIXME: The code that was here previously could not + work. Firstly, it tried to convert a floating point + number into an extended precision format, but only + provided a buffer of 5 littlenums, which was too + small. Secondly, it then didn't deal with the value + converted correctly, just reading out the first 4 + littlenum fields and assuming that could be used + directly. + + I think the code was intended to handle expressions + such as: + + LDR r0, =1.0 + VLDR d0, =55.3 + + but the parsers currently don't permit floating-point + literal values to be written this way, so this code + is probably unreachable. To be safe, we simply + return an error here. */ + + inst.error = _("constant expression not supported"); + return true; } else l = generic_bignum; -- cgit v1.1