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[AArch64] Fix preferred_reload_class for regclass STACK_REG.

The existing AArch64 implementation of preferred_reload_class when called with a destination regclass STACK_REG returns the wider register class GENERAL_REG. This patch changes the behavior such that we only return a narrower class (or NO_REGS) and never return a wider class.

I'll leave this on the list 24h before committing.


2013-10-16  Marcus Shawcroft  <>

        * config/aarch64/aarch64.c (aarch64_preferred_reload_class): Adjust
        handling of STACK_REG.
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index da3962f..7fce7a0 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -4219,9 +4219,18 @@ aarch64_class_max_nregs (reg_class_t regclass, enum machine_mode mode)
 static reg_class_t
 aarch64_preferred_reload_class (rtx x, reg_class_t regclass)
-  if (regclass == POINTER_REGS || regclass == STACK_REG)
+  if (regclass == POINTER_REGS)
     return GENERAL_REGS;
+  if (regclass == STACK_REG)
+    {
+      if (REG_P(x)
+	  && reg_class_subset_p (REGNO_REG_CLASS (REGNO (x)), POINTER_REGS))
+	  return regclass;
+      return NO_REGS;
+    }
   /* If it's an integer immediate that MOVI can't handle, then
      FP_REGS is not an option, so we return NO_REGS instead.  */
   if (CONST_INT_P (x) && reg_class_subset_p (regclass, FP_REGS)

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