[PATCH 3/3] Add targetm.insn_cost hook

[Segher Boessenkool <segher at kernel dot crashing dot org>]

This adds a new hook that the insn_cost function uses if a target has
implemented it (it uses the old pattern_cost nee insn_rtx_cost if not).

I'll commit this now; it was okayed by Jeff at
https://gcc.gnu.org/ml/gcc-patches/2017-08/msg00204.html .


Segher


2017-10-09  Segher Boessenkool  <segher@kernel.crashing.org>

	* target.def (insn_cost): New hook.
	* doc/tm.texi.in (TARGET_INSN_COST): New hook.
	* doc/tm.texi: Regenerate.
	* rtlanal.c (insn_cost): Use the new hook.

---
 gcc/doc/tm.texi    | 12 ++++++++++++
 gcc/doc/tm.texi.in |  2 ++
 gcc/rtlanal.c      |  3 +++
 gcc/target.def     | 14 ++++++++++++++
 4 files changed, 31 insertions(+)

diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 8f503e1..0377217 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -6652,6 +6652,18 @@ should probably only be given to addresses with different numbers of
 registers on machines with lots of registers.
 @end deftypefn
 
+@deftypefn {Target Hook} int TARGET_INSN_COST (rtx_insn *@var{insn}, bool @var{speed})
+This target hook describes the relative costs of RTL instructions.
+
+In implementing this hook, you can use the construct
+@code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast
+instructions.
+
+When optimizing for code size, i.e.@: when @code{speed} is
+false, this target hook should be used to estimate the relative
+size cost of an expression, again relative to @code{COSTS_N_INSNS}.
+@end deftypefn
+
 @deftypefn {Target Hook} {unsigned int} TARGET_MAX_NOCE_IFCVT_SEQ_COST (edge @var{e})
 This hook returns a value in the same units as @code{TARGET_RTX_COSTS},
 giving the maximum acceptable cost for a sequence generated by the RTL
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 15b3f1f..d2cf68f 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -4600,6 +4600,8 @@ Define this macro if a non-short-circuit operation produced by
 
 @hook TARGET_ADDRESS_COST
 
+@hook TARGET_INSN_COST
+
 @hook TARGET_MAX_NOCE_IFCVT_SEQ_COST
 
 @hook TARGET_NOCE_CONVERSION_PROFITABLE_P
diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c
index f01eab5..eadf691 100644
--- a/gcc/rtlanal.c
+++ b/gcc/rtlanal.c
@@ -5329,6 +5329,9 @@ pattern_cost (rtx pat, bool speed)
 int
 insn_cost (rtx_insn *insn, bool speed)
 {
+  if (targetm.insn_cost)
+    return targetm.insn_cost (insn, speed);
+
   return pattern_cost (PATTERN (insn), speed);
 }
 
diff --git a/gcc/target.def b/gcc/target.def
index 80ef746..aac5d27 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -3715,6 +3715,20 @@ registers on machines with lots of registers.",
  int, (rtx address, machine_mode mode, addr_space_t as, bool speed),
  default_address_cost)
 
+/* Compute a cost for INSN.  */
+DEFHOOK
+(insn_cost,
+ "This target hook describes the relative costs of RTL instructions.\n\
+\n\
+In implementing this hook, you can use the construct\n\
+@code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast\n\
+instructions.\n\
+\n\
+When optimizing for code size, i.e.@: when @code{speed} is\n\
+false, this target hook should be used to estimate the relative\n\
+size cost of an expression, again relative to @code{COSTS_N_INSNS}.",
+ int, (rtx_insn *insn, bool speed), NULL)
+
 /* Give a cost, in RTX Costs units, for an edge.  Like BRANCH_COST, but with
    well defined units.  */
 DEFHOOK
-- 
1.8.3.1