[PATCH v2, rtl-optimization]: Fix PR46829, ICE in spill_failure with -fschedule-insns [was: Fixing instability of -fschedule-insns for x86]

[Uros Bizjak <ubizjak at gmail dot com>]

Hello!

After discussion with Oleg, it looks that it is enough to prevent
wrong registers in the output of the (multi-output) insn pattern. As
far as inputs are concerned, combine already handles limited reload
classes in the right way. The problem with x86 is, that reload tried
to fix output operand of the multi-output ins, where scheduler already
moved load of ax register before this insn.

Version 2 of the patch now handles only output operands. Also,
handling of empty constraints was fixed.

2012-08-18  Uros Bizjak  <ubizjak@gmail.com>

	PR rtl-optimization/46829
	* combine.c (recog_for_combine): Check operand constraints
	to reject instructions where wrong hard registers were propagated
	into output operands.

testsuite/ChangeLog:

2012-08-18  Uros Bizjak  <ubizjak@gmail.com>

	PR rtl-optimization/46829
	* gcc.target/i386/pr46829.c: New test.

Patch was bootstrapped and regression tested on
x86_64-unknown-linux-gnu {,-m32}.

Uros.

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