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[PATCH] [MSP430] Fix gcc.dg/pr85180.c and gcc.dg/pr87985.c timeouts for msp430-elf -mlarge


Compilation of gcc.dg/pr85180.c and gcc.dg/pr87985.c times out after 5 minutes
for msp430 with -mlarge.

nonzero_bits1 (from rtlanal.c), recurses many times for each reg
because reg_nonzero_bits_for_combine (combine.c) never considers using 
last_set_nonzero_bits for the given reg when the reg is PSImode (i.e. Pmode for
msp430-elf -mlarge).

nonzero bits for a mode of class MODE_PARTIAL_INT are valid for a mode of class
MODE_INT, and vice-versa. The existing comment in reg_nonzero_bits_for_combine
explaining why last_set_nonzero_bits is valid even when the precision of the
last set mode is less than the current mode, also explains why
MODE_PARTIAL_INT and MODE_INT can be used interchangeably here:

> record_value_for_reg invoked nonzero_bits on the register
> with nonzero_bits_mode (because last_set_mode is necessarily integral
> and HWI_COMPUTABLE_MODE_P in this case) so bits in nonzero_bits_mode
> are all valid, hence in mode too since nonzero_bits_mode is defined
> to the largest HWI_COMPUTABLE_MODE_P mode.

The attached patch fixes the timeout with mlarge (compilation takes only a
couple of seconds) by allowing the last set nonzero bits for a 
reg to be used if either the current mode or last mode is
MODE_PARTIAL_INT or MODE_INT. Currently only MODE_INT is considered.

Successfully bootstrapped and regtested x86_64-pc-linux-gnu and msp430-elf
-msmall and -mlarge.

Ok for trunk?
>From 753dbbfab665020cece59496765086b3debe23f9 Mon Sep 17 00:00:00 2001
From: Jozef Lawrynowicz <jozef.l@mittosystems.com>
Date: Tue, 27 Nov 2018 19:03:53 +0000
Subject: [PATCH] Use last_set_nonzero_bits for a REG when REG mode is
 MODE_PARTIAL_INT

2018-12-12  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	gcc/ChangeLog:

	* combine.c (reg_nonzero_bits_for_combine): Use last_set_nonzero_bits
	for a reg if the current mode or last set mode was MODE_PARTIAL_INT.

---
 gcc/combine.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/gcc/combine.c b/gcc/combine.c
index 7e61139..73b80b6 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -10245,8 +10245,10 @@ reg_nonzero_bits_for_combine (const_rtx x, scalar_int_mode xmode,
   if (rsp->last_set_value != 0
       && (rsp->last_set_mode == mode
 	  || (REGNO (x) >= FIRST_PSEUDO_REGISTER
-	      && GET_MODE_CLASS (rsp->last_set_mode) == MODE_INT
-	      && GET_MODE_CLASS (mode) == MODE_INT))
+	      && (GET_MODE_CLASS (rsp->last_set_mode) == MODE_INT
+		  || GET_MODE_CLASS (rsp->last_set_mode) == MODE_PARTIAL_INT)
+	      && (GET_MODE_CLASS (mode) == MODE_INT
+		  || GET_MODE_CLASS (mode) == MODE_PARTIAL_INT)))
       && ((rsp->last_set_label >= label_tick_ebb_start
 	   && rsp->last_set_label < label_tick)
 	  || (rsp->last_set_label == label_tick
-- 
2.7.4


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