simplify-rtx.c (simplify_unary_operation_1 <case TRUNCATE>): A truncate of a…

simplify-rtx.c (simplify_unary_operation_1 <case TRUNCATE>): A truncate of a memory is just loading the low part of the memory.

2012-09-01  Andrew Pinski  <apinski@cavium.com>

	* simplify-rtx.c (simplify_unary_operation_1 <case TRUNCATE>):
	A truncate of a memory is just loading the low part of the memory.

2012-09-01  Andrew Pinski  <apinski@cavium.com>

        * gcc.target/mips/truncate-8.c: New testcase.

From-SVN: r190848

gcc/ChangeLog

+2012-09-01  Andrew Pinski  <apinski@cavium.com>
+
+	* simplify-rtx.c (simplify_unary_operation_1 <case TRUNCATE>):
+	A truncate of a memory is just loading the low part of the memory.
+
 2012-09-01  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/46829

gcc/simplify-rtx.c

@@ -869,6 +869,14 @@ simplify_unary_operation_1 (enum rtx_code code, enum machine_mode mode, rtx op)
 	  && COMPARISON_P (op)
 	  && (STORE_FLAG_VALUE & ~GET_MODE_MASK (mode)) == 0)
 	return rtl_hooks.gen_lowpart_no_emit (mode, op);
+
+      /* A truncate of a memory is just loading the low part of the memory
+	 if we are not changing the meaning of the address. */
+      if (GET_CODE (op) == MEM
+	  && !MEM_VOLATILE_P (op)
+	  && !mode_dependent_address_p (XEXP (op, 0)))
+	return rtl_hooks.gen_lowpart_no_emit (mode, op);
+
       break;
 
     case FLOAT_TRUNCATE:

gcc/testsuite/ChangeLog

+2012-09-01  Andrew Pinski  <apinski@cavium.com>
+
+	* gcc.target/mips/truncate-8.c: New testcase.
+
 2012-09-01  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/46829

gcc/testsuite/gcc.target/mips/truncate-8.c

+/* { dg-options "-mgp64" } */
+/* { dg-skip-if "code quality test" { *-*-* } { "-O0" } { "" } } */
+/* { dg-final { scan-assembler "\tlw\t" } } */
+/* { dg-final { scan-assembler-not "\tsll\t" } } */
+/* { dg-final { scan-assembler-not "\tld\t" } } */
+
+struct s
+{
+  long long a;
+  int b;
+};
+
+int
+foo (struct s *x)
+{
+  return x->a;
+}
+