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Fix PR rtl-optimization/81803
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Tue, 31 Oct 2017 19:28 +0100
- Subject: Fix PR rtl-optimization/81803
- Authentication-results: sourceware.org; auth=none
This is a regression present on the mainline and 7 branch for little-endian
64-bit MIPS platforms under the form of incorrect spill/reload pairs generated
by the LRA pass, i.e. for which the spill instruction is a narrower access
than the reload instruction. That's incorrect for accesses no wider than a
word on WORD_REGISTER_OPERATIONS target because all the bits up to the word
size need to be preserved.
The attached patch fixes the problem by mimicing in curr_insn_transform what
push_reload does for SUBREGs no wider than a word for WORD_REGISTER_OPERATIONS
targets, i.e. reloading the whole register and not just the subreg.
Tested on SPARC64/Linux and ARM/EABI (both WORD_REGISTER_OPERATIONS targets).
Unfortunately I don't have access to MIPS hardware anymore and the PR doesn't
contain any executable testcase.
Applied on the mainline only for now.
2017-10-31 Matthew Fortune <matthew.fortune@imgtec.com>
Eric Botcazou <ebotcazou@adacore.com>
PR rtl-optimization/81803
* lra-constraints.c (curr_insn_transform): Also reload the whole
register for a strict subreg no wider than a word if this is for
a WORD_REGISTER_OPERATIONS target.
--
Eric BotcazouIndex: lra-constraints.c
===================================================================
--- lra-constraints.c (revision 254193)
+++ lra-constraints.c (working copy)
@@ -4207,8 +4207,9 @@ curr_insn_transform (bool check_only_p)
reg = SUBREG_REG (*loc);
byte = SUBREG_BYTE (*loc);
if (REG_P (reg)
- /* Strict_low_part requires reload the register not
- the sub-register. */
+ /* Strict_low_part requires reloading the register and not
+ just the subreg. Likewise for a strict subreg no wider
+ than a word for WORD_REGISTER_OPERATIONS targets. */
&& (curr_static_id->operand[i].strict_low
|| (!paradoxical_subreg_p (mode, GET_MODE (reg))
&& (hard_regno
@@ -4219,7 +4220,11 @@ curr_insn_transform (bool check_only_p)
&& (goal_alt[i] == NO_REGS
|| (simplify_subreg_regno
(ira_class_hard_regs[goal_alt[i]][0],
- GET_MODE (reg), byte, mode) >= 0)))))
+ GET_MODE (reg), byte, mode) >= 0)))
+ || (GET_MODE_PRECISION (mode)
+ < GET_MODE_PRECISION (GET_MODE (reg))
+ && GET_MODE_SIZE (GET_MODE (reg)) <= UNITS_PER_WORD
+ && WORD_REGISTER_OPERATIONS)))
{
/* An OP_INOUT is required when reloading a subreg of a
mode wider than a word to ensure that data beyond the