Hello!
Attached patch fixes oversight in standard_x87sse_constant_load
splitter and its float-extend counterpart, where a FP reg-reg move
insn RTX can be tagged with REG_EQUIV or REG_EQUAL const_double RTX.
find_constant_src and ix86_standard_x87sse_constant_load_p predicate
are able to handle this situation, and patched splitters emit direct
constant load instead of a reg-reg move. This also lowers regstack
register pressure, as evident from the testcase:
--- pr79593.s_ 2017-02-21 19:41:36.615740647 +0100
+++ pr79593.s 2017-02-21 19:41:47.251622966 +0100
@@ -15,21 +15,16 @@
fldz
.L2:
fld1
- fld %st(0)
- fcomp %st(2)
+ fcomp %st(1)
fnstsw %ax
sahf
- jnb .L5
- fstp %st(1)
- jmp .L3
- .p2align 4,,10
- .p2align 3
-.L5:
+ jnb .L3
fstp %st(0)
+ fld1
.L3:
rep ret
.cfi_endproc
.LFE2:
.size bar, .-bar
- .ident "GCC: (GNU) 7.0.0 20170117 (experimental) [trunk
revision 244540]"
+ .ident "GCC: (GNU) 7.0.1 20170221 (experimental) [trunk
revision 245630]"
.section .note.GNU-stack,"",@progbits
Patched compiler also removed a jump to a BB where only compensating
regstack pop was emitted.
2017-02-21 Uros Bizjak <ubiz...@gmail.com>
PR target/79593
* config/i386/i386.md (standard_x87sse_constant_load splitter):
Use nonimmediate_operand instead of memory_operand for operand 1.
(float-extend standard_x87sse_constant_load splitter): Ditto.
testsuite/ChangeLog:
2017-02-21 Uros Bizjak <ubiz...@gmail.com>
PR target/79593
* gcc.target/i386/pr79593.c: New test.
Patch was bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
Committed to mainline SVN.
Uros.
