There shouldn't be many cases in which a useful hard register is
live across a call before RA, so we might as well keep things simple
and invalidate partially-clobbered registers here, in case the values
they hold leak into the call-clobbered part.  In principle this is
but in practice it probably doesn't make a difference.

2019-09-11  Richard Sandiford  <>

        * combine.c: Include function-abi.h.
        (record_dead_and_set_regs): Use call_insn_abi to get the ABI
        of call insns.  Invalidate partially-clobbered registers as
        well as fully-clobbered ones.

Index: gcc/combine.c
--- gcc/combine.c       2019-09-09 18:58:51.448270881 +0100
+++ gcc/combine.c       2019-09-11 19:47:57.062032638 +0100
@@ -105,6 +105,7 @@ Software Foundation; either version 3, o
 #include "valtrack.h"
 #include "rtl-iter.h"
 #include "print-rtl.h"
+#include "function-abi.h"
 /* Number of attempts to combine instructions in this function.  */
@@ -13464,11 +13465,21 @@ record_dead_and_set_regs (rtx_insn *insn
   if (CALL_P (insn))
+      function_abi abi = call_insn_abi (insn);
       hard_reg_set_iterator hrsi;
-      EXECUTE_IF_SET_IN_HARD_REG_SET (regs_invalidated_by_call, 0, i, hrsi)
+      EXECUTE_IF_SET_IN_HARD_REG_SET (abi.full_and_partial_reg_clobbers (),
+                                     0, i, hrsi)
          reg_stat_type *rsp;
+         /* ??? We could try to preserve some information from the last
+            set of register I if the call doesn't actually clobber
+            (reg:last_set_mode I), which might be true for ABIs with
+            partial clobbers.  However, it would be difficult to
+            update last_set_nonzero_bits and last_sign_bit_copies
+            to account for the part of I that actually was clobbered.
+            It wouldn't help much anyway, since we rarely see this
+            situation before RA.  */
          rsp = &reg_stat[i];
          rsp->last_set_invalid = 1;
          rsp->last_set = insn;

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