https://gcc.gnu.org/g:44e61bd7124c762e81d8c6e615fbe7c88f773637
commit r15-6432-g44e61bd7124c762e81d8c6e615fbe7c88f773637
Author: Jiahao Xu <xujia...@loongson.cn>
Date: Tue Dec 17 10:41:48 2024 +0800
LoongArch: Implement TARGET_IRA_CHANGE_PSEUDO_ALLOCNO_CLASS hook
The hook changes the allocno class to either FP_REGS or GR_REGS depending on
the mode of the register. This results in better register allocation
overall,
fewer spills and reduced codesize - particularly in SPEC2017 lbm.
gcc/ChangeLog:
* config/loongarch/loongarch.cc
(loongarch_ira_change_pseudo_allocno_class): New function.
(TARGET_IRA_CHANGE_PSEUDO_ALLOCNO_CLASS): Define macro.
Diff:
---
gcc/config/loongarch/loongarch.cc | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/gcc/config/loongarch/loongarch.cc
b/gcc/config/loongarch/loongarch.cc
index 861558f07bcc..125ecc26c9cd 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -6989,6 +6989,40 @@ loongarch_secondary_reload (bool in_p ATTRIBUTE_UNUSED,
rtx x,
return NO_REGS;
}
+/* Implement TARGET_IRA_CHANGE_PSEUDO_ALLOCNO_CLASS.
+
+ The register allocator chooses ALL_REGS if FP_REGS and GR_REGS have the
+ same cost - even if ALL_REGS has a much higher cost. ALL_REGS is also used
+ if the cost of both FP_REGS and GR_REGS is lower than the memory cost (in
+ this case the best class is the lowest cost one). Using ALL_REGS
+ irrespectively of itself cost results in bad allocations with many redundant
+ int<->FP moves which are expensive on various cores.
+
+ To avoid this we don't allow ALL_REGS as the allocno class, but force a
+ decision between FP_REGS and GR_REGS. We use the allocno class if it isn't
+ ALL_REGS. Similarly, use the best class if it isn't ALL_REGS. Otherwise
Set
+ the allocno class depending on the mode.
+
+ This change has a similar effect to increasing the cost of FPR->GPR register
+ moves for integer modes so that they are higher than the cost of memory but
+ changing the allocno class is more reliable. */
+
+static reg_class_t
+loongarch_ira_change_pseudo_allocno_class (int regno, reg_class_t
allocno_class,
+ reg_class_t best_class)
+{
+ enum machine_mode mode;
+
+ if (allocno_class != ALL_REGS)
+ return allocno_class;
+
+ if (best_class != ALL_REGS)
+ return best_class;
+
+ mode = PSEUDO_REGNO_MODE (regno);
+ return FLOAT_MODE_P (mode) || VECTOR_MODE_P (mode) ? FP_REGS : GR_REGS;
+}
+
/* Implement TARGET_VALID_POINTER_MODE. */
static bool
@@ -11148,6 +11182,10 @@ loongarch_asm_code_end (void)
#undef TARGET_SECONDARY_RELOAD
#define TARGET_SECONDARY_RELOAD loongarch_secondary_reload
+#undef TARGET_IRA_CHANGE_PSEUDO_ALLOCNO_CLASS
+#define TARGET_IRA_CHANGE_PSEUDO_ALLOCNO_CLASS \
+ loongarch_ira_change_pseudo_allocno_class
+
#undef TARGET_HAVE_SPECULATION_SAFE_VALUE
#define TARGET_HAVE_SPECULATION_SAFE_VALUE speculation_safe_value_not_needed
