gas: use literals/const16 for xtensa loop relaxation

Loop opcode relaxation that uses addi/addmi doesn't work well with other
relaxations that may cause code movement. Instead of encoding fixed loop
end offset in the relaxed sequence use l32r or a pair of const16 to load
loop end address. This way the address of the loop end gets a relocation
record and it gets updated appropriately.

gas/
2019-04-03  Max Filippov  <jcmvbkbc@gmail.com>

	* config/tc-xtensa.c (convert_frag_immed): Drop
	convert_frag_immed_finish_loop invocation.
	(convert_frag_immed_finish_loop): Drop declaration and
	definition.
	* config/xtensa-relax.c (widen_spec_list): Replace loop
	widening that uses addi/addmi with widening that uses l32r
	and const16.

1 files changed, 55 insertions, 22 deletions

diff --git a/gas/config/xtensa-relax.c b/gas/config/xtensa-relax.c
index cb296ed..daf15d5 100644
--- a/gas/config/xtensa-relax.c
+++ b/gas/config/xtensa-relax.c
@@ -87,13 +87,7 @@
    when the first and second operands are not the same as specified
    by the "| %at!=%as" precondition clause.
    {"l32i %at,%as,%imm | %at!=%as",
-   "LITERAL %imm; l32r %at,%LITERAL; add %at,%at,%as; l32i %at,%at,0"}
-
-   There is special case for loop instructions here, but because we do
-   not currently have the ability to represent the difference of two
-   symbols, the conversion requires special code in the assembler to
-   write the operands of the addi/addmi pair representing the
-   difference of the old and new loop end label.  */
+   "LITERAL %imm; l32r %at,%LITERAL; add %at,%at,%as; l32i %at,%at,0"}  */
 
 #include "as.h"
 #include "xtensa-isa.h"
@@ -306,44 +300,83 @@ static string_pattern_pair widen_spec_list[] =
   {"l32i %at,%as,%imm | %at!=%as ? IsaUseConst16",
    "const16 %at,HI16U(%imm); const16 %at,LOW16U(%imm); add %at,%at,%as; l32i %at,%at,0"},
 
-  /* This is only PART of the loop instruction.  In addition,
-     hardcoded into its use is a modification of the final operand in
-     the instruction in bytes 9 and 12.  */
-  {"loop %as,%label | %as!=1 ? IsaUseLoops",
+  /* Widening loops with literals.  */
+  {"loop %as,%label | %as!=1 ? IsaUseLoops ? IsaUseL32R",
+   "loop %as,%LABEL;"
+   "rsr.lend    %as;"		/* LEND */
+   "wsr.lbeg    %as;"		/* LBEG */
+   "LITERAL     %label;"
+   "l32r        %as, %LITERAL;"
+   "nop;"
+   "wsr.lend    %as;"
+   "isync;"
+   "rsr.lcount    %as;"		/* LCOUNT */
+   "addi    %as, %as, 1;"
+   "LABEL"},
+  {"loopgtz %as,%label | %as!=1 ? IsaUseLoops ? IsaUseL32R",
+   "beqz    %as,%label;"
+   "bltz    %as,%label;"
+   "loopgtz %as,%LABEL;"
+   "rsr.lend    %as;"		/* LEND */
+   "wsr.lbeg    %as;"		/* LBEG */
+   "LITERAL     %label;"
+   "l32r        %as, %LITERAL;"
+   "nop;"
+   "wsr.lend    %as;"
+   "isync;"
+   "rsr.lcount    %as;"		/* LCOUNT */
+   "addi    %as, %as, 1;"
+   "LABEL"},
+  {"loopnez %as,%label | %as!=1 ? IsaUseLoops ? IsaUseL32R",
+   "beqz     %as,%label;"
+   "loopnez %as,%LABEL;"
+   "rsr.lend    %as;"		/* LEND */
+   "wsr.lbeg    %as;"		/* LBEG */
+   "LITERAL     %label;"
+   "l32r        %as, %LITERAL;"
+   "nop;"
+   "wsr.lend    %as;"
+   "isync;"
+   "rsr.lcount    %as;"		/* LCOUNT */
+   "addi    %as, %as, 1;"
+   "LABEL"},
+
+  /* Widening loops with const16.  */
+  {"loop %as,%label | %as!=1 ? IsaUseLoops ? IsaUseConst16",
    "loop %as,%LABEL;"
    "rsr.lend    %as;"		/* LEND */
    "wsr.lbeg    %as;"		/* LBEG */
-   "addi    %as, %as, 0;"	/* lo8(%label-%LABEL1) */
-   "addmi   %as, %as, 0;"	/* mid8(%label-%LABEL1) */
+   "const16     %as,HI16U(%label);"
+   "const16     %as,LOW16U(%label);"
    "wsr.lend    %as;"
    "isync;"
    "rsr.lcount    %as;"		/* LCOUNT */
-   "addi    %as, %as, 1;"	/* density -> addi.n %as, %as, 1 */
+   "addi    %as, %as, 1;"
    "LABEL"},
-  {"loopgtz %as,%label | %as!=1 ? IsaUseLoops",
+  {"loopgtz %as,%label | %as!=1 ? IsaUseLoops ? IsaUseConst16",
    "beqz    %as,%label;"
    "bltz    %as,%label;"
    "loopgtz %as,%LABEL;"
    "rsr.lend    %as;"		/* LEND */
    "wsr.lbeg    %as;"		/* LBEG */
-   "addi    %as, %as, 0;"	/* lo8(%label-%LABEL1) */
-   "addmi   %as, %as, 0;"	/* mid8(%label-%LABEL1) */
+   "const16     %as,HI16U(%label);"
+   "const16     %as,LOW16U(%label);"
    "wsr.lend    %as;"
    "isync;"
    "rsr.lcount    %as;"		/* LCOUNT */
-   "addi    %as, %as, 1;"	/* density -> addi.n %as, %as, 1 */
+   "addi    %as, %as, 1;"
    "LABEL"},
-  {"loopnez %as,%label | %as!=1 ? IsaUseLoops",
+  {"loopnez %as,%label | %as!=1 ? IsaUseLoops ? IsaUseConst16",
    "beqz     %as,%label;"
    "loopnez %as,%LABEL;"
    "rsr.lend    %as;"		/* LEND */
    "wsr.lbeg    %as;"		/* LBEG */
-   "addi    %as, %as, 0;"	/* lo8(%label-%LABEL1) */
-   "addmi   %as, %as, 0;"	/* mid8(%label-%LABEL1) */
+   "const16     %as,HI16U(%label);"
+   "const16     %as,LOW16U(%label);"
    "wsr.lend    %as;"
    "isync;"
    "rsr.lcount    %as;"		/* LCOUNT */
-   "addi    %as, %as, 1;"	/* density -> addi.n %as, %as, 1 */
+   "addi    %as, %as, 1;"
    "LABEL"},
 
   /* Relaxing to wide branches.  Order is important here.  With wide