Eric Botcazou <ebotca...@adacore.com> writes: > SUBREG and ZERO_EXTEND of CONST_INTs are treated somewhat specially in the > entire file, see for example do_SUBST. This isn't the case for other unary > operators, presumably because this isn't really necessary here. So I'm not > convinced that such a generalization is really a good thing in this case.
OK. The version below just adds a special case tomake_compound_operation instead. As before, I've restricted the simplification to constants, so that we don't inadvertently undo the effects of m_c_o itself. Tested on x86_64-linux-gnu and mips-linux-gnu. OK for trunk? Richard gcc/ PR rtl-optimization/49145 * combine.c (make_compound_operation): Handle ZERO_EXTEND specially. gcc/testsuite/ PR rtl-optimization/49145 From Ryan Mansfield * gcc.c-torture/compile/pr49145.c: New test. Index: gcc/combine.c =================================================================== --- gcc/combine.c 2011-06-01 22:09:09.000000000 +0100 +++ gcc/combine.c 2011-06-01 22:09:26.000000000 +0100 @@ -7881,7 +7881,20 @@ make_compound_operation (rtx x, enum rtx code = GET_CODE (x); } - /* Now recursively process each operand of this operation. */ + /* Now recursively process each operand of this operation. We need to + handle ZERO_EXTEND specially so that we don't lose track of the + inner mode. */ + if (GET_CODE (x) == ZERO_EXTEND) + { + new_rtx = make_compound_operation (XEXP (x, 0), next_code); + tem = simplify_const_unary_operation (ZERO_EXTEND, GET_MODE (x), + new_rtx, GET_MODE (XEXP (x, 0))); + if (tem) + return tem; + SUBST (XEXP (x, 0), new_rtx); + return x; + } + fmt = GET_RTX_FORMAT (code); for (i = 0; i < GET_RTX_LENGTH (code); i++) if (fmt[i] == 'e') Index: gcc/testsuite/gcc.c-torture/compile/pr49145.c =================================================================== --- /dev/null 2011-06-04 08:47:56.158317425 +0100 +++ gcc/testsuite/gcc.c-torture/compile/pr49145.c 2011-06-01 22:09:26.000000000 +0100 @@ -0,0 +1,30 @@ +static int +func1 (int a, int b) +{ + return b ? a : a / b; +} + +static unsigned char +func2 (unsigned char a, int b) +{ + return b ? a : b; +} + +int i; + +void +func3 (const int arg) +{ + for (i = 0; i != 10; i = foo ()) + { + if (!arg) + { + int j; + for (j = 0; j < 5; j += 1) + { + int *ptr; + *ptr = func2 (func1 (arg, *ptr), foo (arg)); + } + } + } +}