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[PATCH] Fix ICE during insv expansion (PR rtl-optimization/70174)


Hi!

The following testcase ICEs on i?86/x86_64 and aarch64, because gen_lowpart
(pointer to gen_lowpart_general at that spot) doesn't want to handle
SUBREG of SYMBOL_REF.  Fixed by using a variant that doesn't ICE and forcing
the operand into a register if it can't be optimized without generating
instructions.  This is similar to the case a few lines above, where we also
force_reg if simplify_subreg failed.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2016-03-11  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/70174
	* expmed.c (store_bit_field_using_insv): Use gen_lowpart_if_possible
	followed by gen_lowpart on force_reg instead of just gen_lowpart.

	* gcc.dg/pr70174.c: New test.

--- gcc/expmed.c.jj	2016-02-11 20:28:51.000000000 +0100
+++ gcc/expmed.c	2016-03-11 10:40:27.258719168 +0100
@@ -658,24 +658,28 @@ store_bit_field_using_insv (const extrac
     {
       if (GET_MODE_BITSIZE (GET_MODE (value)) >= bitsize)
 	{
+	  rtx tmp;
 	  /* Optimization: Don't bother really extending VALUE
 	     if it has all the bits we will actually use.  However,
 	     if we must narrow it, be sure we do it correctly.  */
 
 	  if (GET_MODE_SIZE (GET_MODE (value)) < GET_MODE_SIZE (op_mode))
 	    {
-	      rtx tmp;
-
 	      tmp = simplify_subreg (op_mode, value1, GET_MODE (value), 0);
 	      if (! tmp)
 		tmp = simplify_gen_subreg (op_mode,
 					   force_reg (GET_MODE (value),
 						      value1),
 					   GET_MODE (value), 0);
-	      value1 = tmp;
 	    }
 	  else
-	    value1 = gen_lowpart (op_mode, value1);
+	    {
+	      tmp = gen_lowpart_if_possible (op_mode, value1);
+	      if (! tmp)
+		tmp = gen_lowpart (op_mode, force_reg (GET_MODE (value),
+						       value1));
+	    }
+	  value1 = tmp;
 	}
       else if (CONST_INT_P (value))
 	value1 = gen_int_mode (INTVAL (value), op_mode);
--- gcc/testsuite/gcc.dg/pr70174.c.jj	2016-03-11 10:42:45.914894656 +0100
+++ gcc/testsuite/gcc.dg/pr70174.c	2016-03-11 10:42:31.000000000 +0100
@@ -0,0 +1,11 @@
+/* PR rtl-optimization/70174 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+struct S { int f : 4; } a;
+  
+void
+foo (void)
+{ 
+  a.f = foo;	/* { dg-warning "assignment makes integer from pointer without a cast" } */
+}

	Jakub


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