simplify-rtx: Put simplify routines into a class

One of the recurring warts of RTL is that multiplication by a power
of 2 is represented as a MULT inside a MEM but as an ASHIFT outside
a MEM.  It would obviously be better if we didn't have this kind of
context sensitivity, but it would be difficult to remove.

Currently the simplify-rtx.c routines are hard-coded for the
ASHIFT form.  This means that some callers have to convert the
ASHIFTs “back” into MULTs after calling the simplify-rtx.c
routines; see fwprop.c:canonicalize_address for an example.

I think we can relieve some of the pain by wrapping the simplify-rtx.c
routines in a simple class that tracks whether the expression occurs
in a MEM or not, so that no post-processing is needed.

An obvious concern is whether passing the “this” pointer around
will slow things down or bloat the code.  I can't measure any
increase in compile time after applying the patch.  Sizewise,
simplify-rtx.o text increases by 2.3% in default-checking builds
and 4.1% in release-checking builds.

I realise the MULT/ASHIFT thing isn't the most palatable
reason for doing this, but I think it might be useful for
other things in future, such as using local nonzero_bits
hooks/virtual functions instead of the global hooks.

The obvious alternative would be to add a static variable
and hope that it is always updated correctly.

Later patches make use of this.

gcc/
	* rtl.h (simplify_context): New class.
	(simplify_unary_operation, simplify_binary_operation): Use it.
	(simplify_ternary_operation, simplify_relational_operation): Likewise.
	(simplify_subreg, simplify_gen_unary, simplify_gen_binary): Likewise.
	(simplify_gen_ternary, simplify_gen_relational): Likewise.
	(simplify_gen_subreg, lowpart_subreg): Likewise.
	* simplify-rtx.c (simplify_gen_binary): Turn into a member function
	of simplify_context.
	(simplify_gen_unary, simplify_gen_ternary, simplify_gen_relational)
	(simplify_truncation, simplify_unary_operation): Likewise.
	(simplify_unary_operation_1, simplify_byte_swapping_operation)
	(simplify_associative_operation, simplify_logical_relational_operation)
	(simplify_binary_operation, simplify_binary_operation_series)
	(simplify_distributive_operation, simplify_plus_minus): Likewise.
	(simplify_relational_operation, simplify_relational_operation_1)
	(simplify_cond_clz_ctz, simplify_merge_mask): Likewise.
	(simplify_ternary_operation, simplify_subreg, simplify_gen_subreg)
	(lowpart_subreg): Likewise.
	(simplify_binary_operation_1): Likewise.  Test mem_depth when
	deciding whether the ASHIFT or MULT form is canonical.
	(simplify_merge_mask): Use simplify_context.

1 files changed, 131 insertions, 18 deletions

diff --git a/gcc/rtl.h b/gcc/rtl.h
index 5a1670f..e9df95b 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -3375,30 +3375,143 @@ extern rtx_insn *try_split (rtx, rtx_insn *, int);
 extern rtx_insn *split_insns (rtx, rtx_insn *);
 
 /* In simplify-rtx.c  */
+
+/* A class that records the context in which a simplification
+   is being mode.  */
+class simplify_context
+{
+public:
+  rtx simplify_unary_operation (rtx_code, machine_mode, rtx, machine_mode);
+  rtx simplify_binary_operation (rtx_code, machine_mode, rtx, rtx);
+  rtx simplify_ternary_operation (rtx_code, machine_mode, machine_mode,
+				  rtx, rtx, rtx);
+  rtx simplify_relational_operation (rtx_code, machine_mode, machine_mode,
+				     rtx, rtx);
+  rtx simplify_subreg (machine_mode, rtx, machine_mode, poly_uint64);
+
+  rtx lowpart_subreg (machine_mode, rtx, machine_mode);
+
+  rtx simplify_merge_mask (rtx, rtx, int);
+
+  rtx simplify_gen_unary (rtx_code, machine_mode, rtx, machine_mode);
+  rtx simplify_gen_binary (rtx_code, machine_mode, rtx, rtx);
+  rtx simplify_gen_ternary (rtx_code, machine_mode, machine_mode,
+			    rtx, rtx, rtx);
+  rtx simplify_gen_relational (rtx_code, machine_mode, machine_mode, rtx, rtx);
+  rtx simplify_gen_subreg (machine_mode, rtx, machine_mode, poly_uint64);
+
+  /* Tracks the level of MEM nesting for the value being simplified:
+     0 means the value is not in a MEM, >0 means it is.  This is needed
+     because the canonical representation of multiplication is different
+     inside a MEM than outside.  */
+  unsigned int mem_depth = 0;
+
+private:
+  rtx simplify_truncation (machine_mode, rtx, machine_mode);
+  rtx simplify_byte_swapping_operation (rtx_code, machine_mode, rtx, rtx);
+  rtx simplify_associative_operation (rtx_code, machine_mode, rtx, rtx);
+  rtx simplify_distributive_operation (rtx_code, machine_mode, rtx, rtx);
+  rtx simplify_logical_relational_operation (rtx_code, machine_mode, rtx, rtx);
+  rtx simplify_binary_operation_series (rtx_code, machine_mode, rtx, rtx);
+  rtx simplify_distribute_over_subregs (rtx_code, machine_mode, rtx, rtx);
+  rtx simplify_shift_const_int (rtx_code, machine_mode, rtx, unsigned int);
+  rtx simplify_plus_minus (rtx_code, machine_mode, rtx, rtx);
+  rtx simplify_cond_clz_ctz (rtx, rtx_code, rtx, rtx);
+
+  rtx simplify_unary_operation_1 (rtx_code, machine_mode, rtx);
+  rtx simplify_binary_operation_1 (rtx_code, machine_mode, rtx, rtx, rtx, rtx);
+  rtx simplify_ternary_operation_1 (rtx_code, machine_mode, machine_mode,
+				    rtx, rtx, rtx);
+  rtx simplify_relational_operation_1 (rtx_code, machine_mode, machine_mode,
+				       rtx, rtx);
+};
+
+inline rtx
+simplify_unary_operation (rtx_code code, machine_mode mode, rtx op,
+			  machine_mode op_mode)
+{
+  return simplify_context ().simplify_unary_operation (code, mode, op,
+						       op_mode);
+}
+
+inline rtx
+simplify_binary_operation (rtx_code code, machine_mode mode, rtx op0, rtx op1)
+{
+  return simplify_context ().simplify_binary_operation (code, mode, op0, op1);
+}
+
+inline rtx
+simplify_ternary_operation (rtx_code code, machine_mode mode,
+			    machine_mode op0_mode, rtx op0, rtx op1, rtx op2)
+{
+  return simplify_context ().simplify_ternary_operation (code, mode, op0_mode,
+							 op0, op1, op2);
+}
+
+inline rtx
+simplify_relational_operation (rtx_code code, machine_mode mode,
+			       machine_mode op_mode, rtx op0, rtx op1)
+{
+  return simplify_context ().simplify_relational_operation (code, mode,
+							    op_mode, op0, op1);
+}
+
+inline rtx
+simplify_subreg (machine_mode outermode, rtx op, machine_mode innermode,
+		 poly_uint64 byte)
+{
+  return simplify_context ().simplify_subreg (outermode, op, innermode, byte);
+}
+
+inline rtx
+simplify_gen_unary (rtx_code code, machine_mode mode, rtx op,
+		    machine_mode op_mode)
+{
+  return simplify_context ().simplify_gen_unary (code, mode, op, op_mode);
+}
+
+inline rtx
+simplify_gen_binary (rtx_code code, machine_mode mode, rtx op0, rtx op1)
+{
+  return simplify_context ().simplify_gen_binary (code, mode, op0, op1);
+}
+
+inline rtx
+simplify_gen_ternary (rtx_code code, machine_mode mode, machine_mode op0_mode,
+		      rtx op0, rtx op1, rtx op2)
+{
+  return simplify_context ().simplify_gen_ternary (code, mode, op0_mode,
+						   op0, op1, op2);
+}
+
+inline rtx
+simplify_gen_relational (rtx_code code, machine_mode mode,
+			 machine_mode op_mode, rtx op0, rtx op1)
+{
+  return simplify_context ().simplify_gen_relational (code, mode, op_mode,
+						      op0, op1);
+}
+
+inline rtx
+simplify_gen_subreg (machine_mode outermode, rtx op, machine_mode innermode,
+		     poly_uint64 byte)
+{
+  return simplify_context ().simplify_gen_subreg (outermode, op,
+						  innermode, byte);
+}
+
+inline rtx
+lowpart_subreg (machine_mode outermode, rtx op, machine_mode innermode)
+{
+  return simplify_context ().lowpart_subreg (outermode, op, innermode);
+}
+
 extern rtx simplify_const_unary_operation (enum rtx_code, machine_mode,
 					   rtx, machine_mode);
-extern rtx simplify_unary_operation (enum rtx_code, machine_mode, rtx,
-				     machine_mode);
 extern rtx simplify_const_binary_operation (enum rtx_code, machine_mode,
 					    rtx, rtx);
-extern rtx simplify_binary_operation (enum rtx_code, machine_mode, rtx,
-				      rtx);
-extern rtx simplify_ternary_operation (enum rtx_code, machine_mode,
-				       machine_mode, rtx, rtx, rtx);
 extern rtx simplify_const_relational_operation (enum rtx_code,
 						machine_mode, rtx, rtx);
-extern rtx simplify_relational_operation (enum rtx_code, machine_mode,
-					  machine_mode, rtx, rtx);
-extern rtx simplify_gen_binary (enum rtx_code, machine_mode, rtx, rtx);
-extern rtx simplify_gen_unary (enum rtx_code, machine_mode, rtx,
-			       machine_mode);
-extern rtx simplify_gen_ternary (enum rtx_code, machine_mode,
-				 machine_mode, rtx, rtx, rtx);
-extern rtx simplify_gen_relational (enum rtx_code, machine_mode,
-				    machine_mode, rtx, rtx);
-extern rtx simplify_subreg (machine_mode, rtx, machine_mode, poly_uint64);
-extern rtx simplify_gen_subreg (machine_mode, rtx, machine_mode, poly_uint64);
-extern rtx lowpart_subreg (machine_mode, rtx, machine_mode);
 extern rtx simplify_replace_fn_rtx (rtx, const_rtx,
 				    rtx (*fn) (rtx, const_rtx, void *), void *);
 extern rtx simplify_replace_rtx (rtx, const_rtx, rtx);