a79048f625
This patch improves the expansion of usubvsi4 by allowing suitable
constants to be passed directly. Unlike normal subtraction, either
operand may be a constant (and indeed I have seen cases where both can
be with LTO enabled). One interesting testcase that improves as a
result of this is:
unsigned f6 (unsigned a)
{
unsigned x;
return __builtin_sub_overflow (5U, a, &x) ? 0 : x;
}
Which previously compiled to:
rsbs r3, r0, #5
cmp r0, #5
movls r0, r3
movhi r0, #0
but now generates the optimal sequence:
rsbs r0, r0, #5
movcc r0, #0
* config/arm/arm.md (usubv<mode>4): Delete expansion.
(usubvsi4): New pattern. Allow some immediate values for inputs.
(usubvdi4): New pattern.
From-SVN: r277187
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