Handle a null lhs in expand_direct_optab_fn (PR85862)

This PR showed that the normal function for expanding directly-mapped
internal functions didn't handle the case in which the call was only
being kept for its side-effects.

2018-05-22  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR middle-end/85862
	* internal-fn.c (expand_direct_optab_fn): Cope with a null lhs.

gcc/testsuite/
	PR middle-end/85862
	* gcc.dg/torture/pr85862.c: New test.

From-SVN: r260504

4 files changed, 26 insertions, 6 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fd57840..5e09013 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2018-05-22  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR middle-end/85862
+	* internal-fn.c (expand_direct_optab_fn): Cope with a null lhs.
+
 2018-05-22  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/85834
diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
index b2c4a31..bb4404e 100644
--- a/gcc/internal-fn.c
+++ b/gcc/internal-fn.c
@@ -2891,14 +2891,15 @@ expand_direct_optab_fn (internal_fn fn, gcall *stmt, direct_optab optab,
   insn_code icode = direct_optab_handler (optab, TYPE_MODE (types.first));
 
   tree lhs = gimple_call_lhs (stmt);
-  tree lhs_type = TREE_TYPE (lhs);
-  rtx lhs_rtx = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
+  rtx lhs_rtx = NULL_RTX;
+  if (lhs)
+    lhs_rtx = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
 
   /* Do not assign directly to a promoted subreg, since there is no
      guarantee that the instruction will leave the upper bits of the
      register in the state required by SUBREG_PROMOTED_SIGN.  */
   rtx dest = lhs_rtx;
-  if (GET_CODE (dest) == SUBREG && SUBREG_PROMOTED_VAR_P (dest))
+  if (dest && GET_CODE (dest) == SUBREG && SUBREG_PROMOTED_VAR_P (dest))
     dest = NULL_RTX;
 
   create_output_operand (&ops[0], dest, insn_data[icode].operand[0].mode);
@@ -2917,7 +2918,7 @@ expand_direct_optab_fn (internal_fn fn, gcall *stmt, direct_optab optab,
     }
 
   expand_insn (icode, nargs + 1, ops);
-  if (!rtx_equal_p (lhs_rtx, ops[0].value))
+  if (lhs_rtx && !rtx_equal_p (lhs_rtx, ops[0].value))
     {
       /* If the return value has an integral type, convert the instruction
 	 result to that type.  This is useful for things that return an
@@ -2931,7 +2932,7 @@ expand_direct_optab_fn (internal_fn fn, gcall *stmt, direct_optab optab,
 	  /* If this is a scalar in a register that is stored in a wider
 	     mode than the declared mode, compute the result into its
 	     declared mode and then convert to the wider mode.  */
-	  gcc_checking_assert (INTEGRAL_TYPE_P (lhs_type));
+	  gcc_checking_assert (INTEGRAL_TYPE_P (TREE_TYPE (lhs)));
 	  rtx tmp = convert_to_mode (GET_MODE (lhs_rtx), ops[0].value, 0);
 	  convert_move (SUBREG_REG (lhs_rtx), tmp,
 			SUBREG_PROMOTED_SIGN (lhs_rtx));
@@ -2940,7 +2941,7 @@ expand_direct_optab_fn (internal_fn fn, gcall *stmt, direct_optab optab,
 	emit_move_insn (lhs_rtx, ops[0].value);
       else
 	{
-	  gcc_checking_assert (INTEGRAL_TYPE_P (lhs_type));
+	  gcc_checking_assert (INTEGRAL_TYPE_P (TREE_TYPE (lhs)));
 	  convert_move (lhs_rtx, ops[0].value, 0);
 	}
     }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9083376..489941c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-05-22  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR middle-end/85862
+	* gcc.dg/torture/pr85862.c: New test.
+
 2018-05-22  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/85834
diff --git a/gcc/testsuite/gcc.dg/torture/pr85862.c b/gcc/testsuite/gcc.dg/torture/pr85862.c
new file mode 100644
index 0000000..39995bc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr85862.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-fexceptions -fnon-call-exceptions" } */
+/* { dg-additional-options "-fexceptions -fnon-call-exceptions -mfma" { target i?86-*-* x86_64-*-* } } */
+
+void
+ki (double nq)
+{
+  double no = 1.1 * nq - nq;
+}