Make ira call df_set_regs_ever_live for extra call-clobbered regs

If we support multiple ABIs in the same translation unit, it can
sometimes be the case that a callee clobbers more registers than
its caller is allowed to.  We need to call df_set_regs_ever_live
on these extra registers so that the prologue and epilogue code
can handle them appropriately.

This patch does that in IRA.  I wanted to avoid another full
instruction walk just for this, so I combined it with the existing
set_paradoxical_subreg walk.  This happens before the first
calculation of elimination offsets.

2019-09-30  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* function-abi.h (function_abi_aggregator): New class.
	* function-abi.cc (function_abi_aggregator::caller_save_regs): New
	function.
	* ira.c (update_equiv_regs_prescan): New function.  Call
	set_paradoxical_subreg here rather than...
	(update_equiv_regs): ...here.
	(ira): Call update_equiv_regs_prescan.

From-SVN: r276339

1 files changed, 21 insertions, 0 deletions

diff --git a/gcc/function-abi.h b/gcc/function-abi.h
index 8dd139e..9bb4d17 100644
--- a/gcc/function-abi.h
+++ b/gcc/function-abi.h
@@ -208,6 +208,27 @@ protected:
   HARD_REG_SET m_mask;
 };
 
+/* This class collects information about the ABIs of functions that are
+   called in a particular region of code.  It is mostly intended to be
+   used as a local variable during an IR walk.  */
+class function_abi_aggregator
+{
+public:
+  function_abi_aggregator () : m_abi_clobbers () {}
+
+  /* Record that the code region calls a function with the given ABI.  */
+  void
+  note_callee_abi (const function_abi &abi)
+  {
+    m_abi_clobbers[abi.id ()] |= abi.full_and_partial_reg_clobbers ();
+  }
+
+  HARD_REG_SET caller_save_regs (const function_abi &) const;
+
+private:
+  HARD_REG_SET m_abi_clobbers[NUM_ABI_IDS];
+};
+
 struct target_function_abi_info
 {
   /* An array of all the target ABIs that are available in this