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[PATCH] Fix widening multiply expansion (PR rtl-optimization/47299)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Mon, 17 Jan 2011 23:20:06 +0100
- Subject: [PATCH] Fix widening multiply expansion (PR rtl-optimization/47299)
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
WIDEN_MULT_EXPR expansion has several issues. One is that subtarget
shouldn't be used for operand expansion of different mode.
Another one is that if (for whatever reason) we end up with non-folded
WIDEN_MULT_EXPR of two constants up to expansion (don't have testcase, but guess with
many -fno-* options might be possible), the expansion code wouldn't work too
well. And the last one (triggered on the attached testcase) is that
if we decide to optimize WIDEN_MULT_EXPR with one constant and one
non-constant, the constant needs to be converted from innermode to the
2xwider mode. For other cases the modes on the insn templates should
ensure the right thing happens.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2011-01-17 Jakub Jelinek <jakub@redhat.com>
PR rtl-optimization/47299
* expr.c (expand_expr_real_2) <case WIDEN_MULT_EXPR>: Don't use
subtarget. Use normal multiplication if both operands are
constants.
* expmed.c (expand_widening_mult): Don't try to optimize constant
multiplication if op0 has VOIDmode. Convert op1 constant to mode
before using it.
* gcc.c-torture/execute/pr47299.c: New test.
--- gcc/expr.c.jj 2011-01-04 13:25:20.000000000 +0100
+++ gcc/expr.c 2011-01-17 12:11:22.215545872 +0100
@@ -7631,10 +7631,10 @@ expand_expr_real_2 (sepops ops, rtx targ
if (optab_handler (this_optab, mode) != CODE_FOR_nothing)
{
if (TYPE_UNSIGNED (TREE_TYPE (treeop0)))
- expand_operands (treeop0, treeop1, subtarget, &op0, &op1,
+ expand_operands (treeop0, treeop1, NULL_RTX, &op0, &op1,
EXPAND_NORMAL);
else
- expand_operands (treeop0, treeop1, subtarget, &op1, &op0,
+ expand_operands (treeop0, treeop1, NULL_RTX, &op1, &op0,
EXPAND_NORMAL);
goto binop3;
}
@@ -7652,7 +7652,8 @@ expand_expr_real_2 (sepops ops, rtx targ
optab other_optab = zextend_p ? smul_widen_optab : umul_widen_optab;
this_optab = zextend_p ? umul_widen_optab : smul_widen_optab;
- if (mode == GET_MODE_2XWIDER_MODE (innermode))
+ if (mode == GET_MODE_2XWIDER_MODE (innermode)
+ && TREE_CODE (treeop0) != INTEGER_CST)
{
if (optab_handler (this_optab, mode) != CODE_FOR_nothing)
{
--- gcc/expmed.c.jj 2010-12-02 13:15:24.000000000 +0100
+++ gcc/expmed.c 2011-01-17 12:20:28.437673228 +0100
@@ -3188,12 +3188,17 @@ expand_widening_mult (enum machine_mode
int unsignedp, optab this_optab)
{
bool speed = optimize_insn_for_speed_p ();
+ rtx cop1;
if (CONST_INT_P (op1)
- && (INTVAL (op1) >= 0
+ && GET_MODE (op0) != VOIDmode
+ && (cop1 = convert_modes (mode, GET_MODE (op0), op1,
+ this_optab == umul_widen_optab))
+ && CONST_INT_P (cop1)
+ && (INTVAL (cop1) >= 0
|| GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT))
{
- HOST_WIDE_INT coeff = INTVAL (op1);
+ HOST_WIDE_INT coeff = INTVAL (cop1);
int max_cost;
enum mult_variant variant;
struct algorithm algorithm;
--- gcc/testsuite/gcc.c-torture/execute/pr47299.c.jj 2011-01-17 12:19:14.120763491 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr47299.c 2011-01-17 12:18:55.000000000 +0100
@@ -0,0 +1,17 @@
+/* PR rtl-optimization/47299 */
+
+extern void abort (void);
+
+__attribute__ ((noinline, noclone)) unsigned short
+foo (unsigned char x)
+{
+ return x * 255;
+}
+
+int
+main ()
+{
+ if (foo (0x40) != 0x3fc0)
+ abort ();
+ return 0;
+}
Jakub