* [sparc] Rotate stack checking loop
@ 2015-11-12 21:52 Eric Botcazou
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From: Eric Botcazou @ 2015-11-12 21:52 UTC (permalink / raw)
To: gcc-patches
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Hi,
this patch rotates the loop generated in the prologue to do stack checking
when -fstack-check is specified, thereby saving one branch instruction. It
was initially implemented as a WHILE loop to match the generic implementation
but can be turned into a DO-WHILE loop because the amount of stack to be
checked is known at compile time (since it's the static part of the frame).
Tested on SPARC/Solaris, to be applied on the mainline.
2015-11-12 Eric Botcazou <ebotcazou@adacore.com>
* config/sparc/sparc.c (sparc_emit_probe_stack_range): Adjust.
(output_probe_stack_range): Rotate the loop and simplify.
--
Eric Botcazou
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Index: config/sparc/sparc.c
===================================================================
--- config/sparc/sparc.c (revision 230204)
+++ config/sparc/sparc.c (working copy)
@@ -5058,9 +5058,9 @@ sparc_emit_probe_stack_range (HOST_WIDE_
emit_stack_probe (plus_constant (Pmode, g1, -size));
}
- /* The run-time loop is made up of 10 insns in the generic case while the
+ /* The run-time loop is made up of 9 insns in the generic case while the
compile-time loop is made up of 4+2*(n-2) insns for n # of intervals. */
- else if (size <= 5 * PROBE_INTERVAL)
+ else if (size <= 4 * PROBE_INTERVAL)
{
HOST_WIDE_INT i;
@@ -5147,41 +5147,33 @@ const char *
output_probe_stack_range (rtx reg1, rtx reg2)
{
static int labelno = 0;
- char loop_lab[32], end_lab[32];
+ char loop_lab[32];
rtx xops[2];
- ASM_GENERATE_INTERNAL_LABEL (loop_lab, "LPSRL", labelno);
- ASM_GENERATE_INTERNAL_LABEL (end_lab, "LPSRE", labelno++);
+ ASM_GENERATE_INTERNAL_LABEL (loop_lab, "LPSRL", labelno++);
+ /* Loop. */
ASM_OUTPUT_INTERNAL_LABEL (asm_out_file, loop_lab);
- /* Jump to END_LAB if TEST_ADDR == LAST_ADDR. */
+ /* TEST_ADDR = TEST_ADDR + PROBE_INTERVAL. */
xops[0] = reg1;
+ xops[1] = GEN_INT (-PROBE_INTERVAL);
+ output_asm_insn ("add\t%0, %1, %0", xops);
+
+ /* Test if TEST_ADDR == LAST_ADDR. */
xops[1] = reg2;
output_asm_insn ("cmp\t%0, %1", xops);
- if (TARGET_ARCH64)
- fputs ("\tbe,pn\t%xcc,", asm_out_file);
- else
- fputs ("\tbe\t", asm_out_file);
- assemble_name_raw (asm_out_file, end_lab);
- fputc ('\n', asm_out_file);
-
- /* TEST_ADDR = TEST_ADDR + PROBE_INTERVAL. */
- xops[1] = GEN_INT (-PROBE_INTERVAL);
- output_asm_insn (" add\t%0, %1, %0", xops);
/* Probe at TEST_ADDR and branch. */
if (TARGET_ARCH64)
- fputs ("\tba,pt\t%xcc,", asm_out_file);
+ fputs ("\tbne,pt\t%xcc,", asm_out_file);
else
- fputs ("\tba\t", asm_out_file);
+ fputs ("\tbne\t", asm_out_file);
assemble_name_raw (asm_out_file, loop_lab);
fputc ('\n', asm_out_file);
xops[1] = GEN_INT (SPARC_STACK_BIAS);
output_asm_insn (" st\t%%g0, [%0+%1]", xops);
- ASM_OUTPUT_INTERNAL_LABEL (asm_out_file, end_lab);
-
return "";
}
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