Ok, after debugging, this looks to be a bug in rs6000_legitimate_address_p().
At the beginning of LRA, we have the following insn:
(insn 520 67 71 5 (set (mem:V16QI (and:DI (reg/f:DI 110 sfp)
(const_int -16 [0xfffffffffffffff0])) [0 MEM <vector(16) char>
[(char *)&a + 16B]+0 S16 A128])
(reg:V16QI 303 [ vect__2.13 ])) "bug.i":10:10 1103 {vsx_movv16qi_64bit}
(expr_list:REG_DEAD (reg:V16QI 303 [ vect__2.13 ])
(nil)))
lra_eliminate() then converts that to:
(insn 520 67 71 5 (set (mem:V16QI (and:DI (plus:DI (reg/f:DI 110 sfp)
(const_int 112 [0x70]))
(const_int -16 [0xfffffffffffffff0])) [0 MEM <vector(16) char>
[(char *)&a + 16B]+0 S16 A128])
(reg:V16QI 303 [ vect__2.13 ])) "bug.i":10:10 1103 {vsx_movv16qi_64bit}
(expr_list:REG_DEAD (reg:V16QI 303 [ vect__2.13 ])
(nil)))
which isn't valid and needs fixing...which is fine. process_address()
then gives us:
(insn 520 67 71 5 (set (mem:V16QI (and:DI (reg:DI 633)
(const_int -16 [0xfffffffffffffff0])) [0 MEM <vector(16) char>
[(char *)&a + 16B]+0 S16 A128])
(reg:V16QI 303 [ vect__2.13 ])) "bug.i":10:10 1103 {vsx_movv16qi_64bit}
(expr_list:REG_DEAD (reg:V16QI 303 [ vect__2.13 ])
(nil)))
...with pseudo 633 being set to plus:DI (reg/f:DI 110 sfp) (const_int 112
[0x70])
which is also good. The bug comes when we now pass insn 520 to
rs6000_legitimate_address_p() and we hit the following code:
/* If this is an unaligned stvx/ldvx type address, discard the outer AND. */
if (VECTOR_MEM_ALTIVEC_P (mode)
&& GET_CODE (x) == AND
&& CONST_INT_P (XEXP (x, 1))
&& INTVAL (XEXP (x, 1)) == -16)
x = XEXP (x, 0);
Our mode is V16QI, so we should execute this code, but we don't. The
problem is that VECTOR_MEM_ALTIVEC_P(mode) checks for
"rs6000_vector_unit[(MODE)] == VECTOR_ALTIVEC" and V16QI mode returns
VECTOR_VSX, so we fail to fall into the code above and end up telling
LRA this isn't a valid address. LRA then attempts to spill this again
and again and...
The following patch fixes the bug for me and I'm regtesting it now:
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -8808,7 +8808,7 @@ rs6000_legitimate_address_p (machine_mode mode, rtx x,
bool reg_ok_strict)
bool quad_offset_p = mode_supports_dq_form (mode);
/* If this is an unaligned stvx/ldvx type address, discard the outer AND. */
- if (VECTOR_MEM_ALTIVEC_P (mode)
+ if (VECTOR_MEM_ALTIVEC_OR_VSX_P (mode)
&& GET_CODE (x) == AND
&& CONST_INT_P (XEXP (x, 1))
&& INTVAL (XEXP (x, 1)) == -16)
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https://bugs.launchpad.net/bugs/1862053
Title:
Compiler gets stuck (or extremely slow) on ppc64el
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