[PATCH][PPC] Fix ICE using power9 with soft-float

[Andrew Stubbs]

The testcase powerpc/fusion3.c causes an ICE when compiled with 
-msoft-float.

The key line in the testcase looks fairly harmless:

    void fusion_float_write (float *p, float f){ p[LARGE] = f; }

The error message look like this:

.../gcc.target/powerpc/fusion3.c: In function 'fusion_float_write':^M
.../gcc.target/powerpc/fusion3.c:12:1: error: unrecognizable insn:^M
(insn 18 4 14 2 (parallel [^M
             (set (mem:SF (plus:SI (plus:SI (reg:SI 3 3 [ p ])^M
                             (const_int 327680 [0x50000]))^M
                         (const_int -29420 [0xffffffffffff8d14])) [1 
MEM[(float *)p_1(D) + 298260B]+0 S4 A32])^M
                 (unspec:SF [^M
                         (reg:SF 4 4 [ f ])^M
                     ] UNSPEC_FUSION_P9))^M
             (clobber (reg/f:SI 3 3 [157]))^M
         ]) 
"/scratch/astubbs/fsf/src/gcc-mainline/gcc/testsuite/gcc.target/powerpc/fusion3.c":12 
-1^M
      (nil))^M

Basically, the problem is that the peephole optimization tries to create 
a Power9 Fusion instruction, but those do not support SF values in 
integer registers (AFAICT).

So, presumably, I need to adjust either the predicate or the condition 
of the peephole rules.

The predicate used is "toc_fusion_or_p9_reg_operand", and this might be 
the root cause, but I don't know the architecture well enough to be 
sure. The predicate code seems to suggest that "toc_fusion", whatever 
that is, should be able to do this, but the insn produced by the 
peephole uses only UNSPEC_FUSION_P9, which does not. Perhaps this 
predicate is inappropriate for the P9 Fusion peephole, or perhaps it 
needs to be taught about this corner case?

In any case, I don't want to change the predicate without being sure 
what it does (here and elsewhere), so the attached patch solves the 
problem by changing the condition.

Is this OK, or do I need to do something less blunt?

Thanks

Andrew
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