Re: [PATCH 2/4] [RS6000] PR69645, -ffixed-reg ignored

[David Edelsohn]

On Mon, Mar 21, 2016 at 9:06 AM, Alan Modra  wrote:
> Treat -ffixed-reg as we do for global asm regs.  The only slightly
> complicated part of this patch is that the rs6000 backend itself sets
> fixed_regs[RS6000_PIC_OFFSET_TABLE_REGNUM] in some cases, which means
> we can't simply test fixed_regs[] to determine whether a reg appeared
> as -ffixed-reg.
>
> PR target/69645
> * config/rs6000/rs6000.c (fixed_reg_p): New function.
> (fixed_regs_p): Rename from global_regs_p.  Call fixed_reg_p.
> Update all uses.

Okay.

Thanks, David

[PATCH 2/4] [RS6000] PR69645, -ffixed-reg ignored

[Alan Modra]

Treat -ffixed-reg as we do for global asm regs.  The only slightly
complicated part of this patch is that the rs6000 backend itself sets
fixed_regs[RS6000_PIC_OFFSET_TABLE_REGNUM] in some cases, which means
we can't simply test fixed_regs[] to determine whether a reg appeared
as -ffixed-reg.

PR target/69645
* config/rs6000/rs6000.c (fixed_reg_p): New function.
(fixed_regs_p): Rename from global_regs_p.  Call fixed_reg_p.
Update all uses.

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 0e570e4..99473bd 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -22996,17 +22996,34 @@ is_altivec_return_reg (rtx reg, void *xyes)
 }
 
 
-/* Look for user-defined global regs in the range FIRST to LAST-1.
-   We should not restore these, and so cannot use lmw or out-of-line
-   restore functions if there are any.  We also can't save them
-   (well, emit frame notes for them), because frame unwinding during
-   exception handling will restore saved registers.  */
+/* Return whether REG is a global user reg or has been specifed by
+   -ffixed-REG.  */
 
 static bool
-global_regs_p (unsigned first, unsigned last)
+fixed_reg_p (int reg)
+{
+  /* Ignore fixed_regs[RS6000_PIC_OFFSET_TABLE_REGNUM] when the
+ backend sets it, overriding anything the user might have given.  */
+  if (reg == RS6000_PIC_OFFSET_TABLE_REGNUM
+  && ((DEFAULT_ABI == ABI_V4 && flag_pic)
+ || (DEFAULT_ABI == ABI_DARWIN && flag_pic)
+ || (TARGET_TOC && TARGET_MINIMAL_TOC)))
+return false;
+
+  return fixed_regs[reg];
+}
+
+/* Look for user-defined global regs or -ffixed- in the range
+   FIRST to LAST-1.  We should not restore these, and so cannot use
+   lmw or out-of-line restore functions if there are any.  We also
+   can't save them (well, emit frame notes for them), because frame
+   unwinding during exception handling will restore saved registers.  */
+
+static bool
+fixed_regs_p (unsigned first, unsigned last)
 {
   while (first < last)
-if (global_regs[first++])
+if (fixed_reg_p (first++))
   return true;
   return false;
 }
@@ -23037,7 +23054,7 @@ rs6000_savres_strategy (rs6000_stack_t *info,
   && !TARGET_POWERPC64
   && !(TARGET_SPE_ABI && info->spe_64bit_regs_used)
   && info->first_gp_reg_save < 31
-  && !global_regs_p (info->first_gp_reg_save, 32))
+  && !fixed_regs_p (info->first_gp_reg_save, 32))
 strategy |= SAVRES_MULTIPLE;
 
   if (crtl->calls_eh_return
@@ -23050,16 +23067,16 @@ rs6000_savres_strategy (rs6000_stack_t *info,
   /* The out-of-line FP routines use double-precision stores;
 we can't use those routines if we don't have such stores.  */
   || (TARGET_HARD_FLOAT && !TARGET_DOUBLE_FLOAT)
-  || global_regs_p (info->first_fp_reg_save, 64))
+  || fixed_regs_p (info->first_fp_reg_save, 64))
 strategy |= SAVE_INLINE_FPRS | REST_INLINE_FPRS;
 
   if (info->first_gp_reg_save == 32
   || (!(strategy & SAVRES_MULTIPLE)
- && global_regs_p (info->first_gp_reg_save, 32)))
+ && fixed_regs_p (info->first_gp_reg_save, 32)))
 strategy |= SAVE_INLINE_GPRS | REST_INLINE_GPRS;
 
   if (info->first_altivec_reg_save == LAST_ALTIVEC_REGNO + 1
-  || global_regs_p (info->first_altivec_reg_save, LAST_ALTIVEC_REGNO + 1))
+  || fixed_regs_p (info->first_altivec_reg_save, LAST_ALTIVEC_REGNO + 1))
 strategy |= SAVE_INLINE_VRS | REST_INLINE_VRS;
 
   /* Define cutoff for using out-of-line functions to save registers.  */

-- 
Alan Modra
Australia Development Lab, IBM