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Subject: [Bug rtl-optimization/53908] [4.6/4.7 Regression] csa removes needed memory load
Date: Tue, 10 Jul 2012 22:50:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53908

--- Comment #5 from Mikael Pettersson <mikpe at it dot uu.se> 2012-07-10 22:50:24 UTC ---
On x86_64-linux the SEGV went away on trunk with r186159:
http://gcc.gnu.org/ml/gcc-cvs/2012-04/msg00108.html
http://gcc.gnu.org/ml/gcc-patches/2012-04/msg00202.html

The patch description makes it sound more like a cleanup than fixing actual
bugs, but when I diff the assembly code for the test case with r186158 and
r186159 I see:

--- pr53908.s-r186158   2012-07-11 00:28:57.000000000 +0200
+++ pr53908.s-r186159   2012-07-11 00:34:32.000000000 +0200
...
        call    is_basic
        testl   %eax, %eax
-       movq    8(%rsp), %rbp
-       js      .L68
-.L29:
+       js      .L29
+.L33:
        movq    users(%rip), %rbx
+       movq    8(%rsp), %rbp
        testq   %rbx, %rbx
...

That is, a load is being moved across a control flow insn.  All other diffs
seem to just be changed label numbers.

I'll give it some more testing tomorrow.