combine: Fix problem with RTL checking

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State New
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  • combine: Fix problem with RTL checking
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Segher Boessenkool Feb. 16, 2018, 1:53 p.m.
As Jakub found, after my recent combine patch at least on x86 problems
show up with RTL checking enabled.  This is because the I2 generated
by a successful instruction combination can write not only a register
but it can also write a paradoxical subreg of one.

This fixes it.

Tested on powerpc64-linux {-m64,-m32} and on x86_64-linux {-m64,-m32},
with --enable-checking=yes,rtl.  Committing it now.


2018-02-16  Segher Boessenkool  <>

	* combine.c (try_combine): When adjusting LOG_LINKS for the destination
	that moved to I2, also allow destinations that are a paradoxical
	subreg (instead of a normal reg).

 gcc/combine.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)



diff --git a/gcc/combine.c b/gcc/combine.c
index c386f3a..cd4aaa4 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -4379,7 +4379,12 @@ 
       if (GET_CODE (x) == PARALLEL)
 	x = XVECEXP (newi2pat, 0, 0);
-      unsigned int regno = REGNO (SET_DEST (x));
+      /* It can only be a SET of a REG or of a paradoxical SUBREG of a REG.  */
+      x = SET_DEST (x);
+      if (paradoxical_subreg_p (x))
+	x = SUBREG_REG (x);
+      unsigned int regno = REGNO (x);
       bool done = false;
       for (rtx_insn *insn = NEXT_INSN (i3);