Remove broken ifcvt code for speculating memory writes
* ifcvt.c (noce_mem_write_may_trap_or_fault_p, noce_can_store_speculate): Delete. (noce_process_if_block): Don't try to handle single MEM stores. * rtl.h (memory_must_be_modified_in_insn_p): Don't declare. * alias.c (memory_must_be_modified_in_insn_p): Delete. From-SVN: r230864
This commit is contained in:
Bernd Schmidt
Bernd Schmidt
parent
136108a158
commit
70927cae31
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@ -1,3 +1,11 @@
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2015-11-25 Bernd Schmidt <bschmidt@redhat.com>
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* ifcvt.c (noce_mem_write_may_trap_or_fault_p,
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noce_can_store_speculate): Delete.
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(noce_process_if_block): Don't try to handle single MEM stores.
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* rtl.h (memory_must_be_modified_in_insn_p): Don't declare.
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* alias.c (memory_must_be_modified_in_insn_p): Delete.
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2015-11-25 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
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PR rtl-optimization/68435
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24
gcc/alias.c
24
gcc/alias.c
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@ -3032,30 +3032,6 @@ set_dest_equal_p (const_rtx set, const_rtx item)
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return rtx_equal_p (dest, item);
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}
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/* Like memory_modified_in_insn_p, but return TRUE if INSN will
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*DEFINITELY* modify the memory contents of MEM. */
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bool
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memory_must_be_modified_in_insn_p (const_rtx mem, const_rtx insn)
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{
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if (!INSN_P (insn))
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return false;
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insn = PATTERN (insn);
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if (GET_CODE (insn) == SET)
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return set_dest_equal_p (insn, mem);
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else if (GET_CODE (insn) == PARALLEL)
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{
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int i;
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for (i = 0; i < XVECLEN (insn, 0); i++)
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{
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rtx sub = XVECEXP (insn, 0, i);
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if (GET_CODE (sub) == SET
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&& set_dest_equal_p (sub, mem))
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return true;
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}
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}
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return false;
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}
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/* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
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array. */
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121
gcc/ifcvt.c
121
gcc/ifcvt.c
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@ -2962,97 +2962,6 @@ noce_operand_ok (const_rtx op)
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return ! may_trap_p (op);
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}
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/* Return true if a write into MEM may trap or fault. */
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static bool
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noce_mem_write_may_trap_or_fault_p (const_rtx mem)
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{
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rtx addr;
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if (MEM_READONLY_P (mem))
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return true;
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if (may_trap_or_fault_p (mem))
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return true;
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addr = XEXP (mem, 0);
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/* Call target hook to avoid the effects of -fpic etc.... */
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addr = targetm.delegitimize_address (addr);
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while (addr)
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switch (GET_CODE (addr))
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{
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case CONST:
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case PRE_DEC:
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case PRE_INC:
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case POST_DEC:
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case POST_INC:
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case POST_MODIFY:
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addr = XEXP (addr, 0);
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break;
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case LO_SUM:
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case PRE_MODIFY:
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addr = XEXP (addr, 1);
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break;
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case PLUS:
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if (CONST_INT_P (XEXP (addr, 1)))
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addr = XEXP (addr, 0);
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else
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return false;
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break;
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case LABEL_REF:
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return true;
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case SYMBOL_REF:
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if (SYMBOL_REF_DECL (addr)
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&& decl_readonly_section (SYMBOL_REF_DECL (addr), 0))
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return true;
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return false;
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default:
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return false;
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}
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return false;
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}
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/* Return whether we can use store speculation for MEM. TOP_BB is the
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basic block above the conditional block where we are considering
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doing the speculative store. We look for whether MEM is set
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unconditionally later in the function. */
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static bool
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noce_can_store_speculate_p (basic_block top_bb, const_rtx mem)
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{
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basic_block dominator;
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for (dominator = get_immediate_dominator (CDI_POST_DOMINATORS, top_bb);
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dominator != NULL;
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dominator = get_immediate_dominator (CDI_POST_DOMINATORS, dominator))
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{
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rtx_insn *insn;
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FOR_BB_INSNS (dominator, insn)
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{
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/* If we see something that might be a memory barrier, we
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have to stop looking. Even if the MEM is set later in
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the function, we still don't want to set it
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unconditionally before the barrier. */
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if (INSN_P (insn)
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&& (volatile_insn_p (PATTERN (insn))
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|| (CALL_P (insn) && (!RTL_CONST_CALL_P (insn)))))
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return false;
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if (memory_must_be_modified_in_insn_p (mem, insn))
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return true;
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if (modified_in_p (XEXP (mem, 0), insn))
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return false;
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}
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}
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return false;
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}
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/* Return true if X contains a MEM subrtx. */
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static bool
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@ -3582,30 +3491,12 @@ noce_process_if_block (struct noce_if_info *if_info)
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}
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if (!set_b && MEM_P (orig_x))
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{
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/* Disallow the "if (...) x = a;" form (implicit "else x = x;")
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for optimizations if writing to x may trap or fault,
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i.e. it's a memory other than a static var or a stack slot,
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is misaligned on strict aligned machines or is read-only. If
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x is a read-only memory, then the program is valid only if we
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avoid the store into it. If there are stores on both the
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THEN and ELSE arms, then we can go ahead with the conversion;
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either the program is broken, or the condition is always
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false such that the other memory is selected. */
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if (noce_mem_write_may_trap_or_fault_p (orig_x))
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return FALSE;
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/* Avoid store speculation: given "if (...) x = a" where x is a
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MEM, we only want to do the store if x is always set
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somewhere in the function. This avoids cases like
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if (pthread_mutex_trylock(mutex))
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++global_variable;
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where we only want global_variable to be changed if the mutex
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is held. FIXME: This should ideally be expressed directly in
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RTL somehow. */
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if (!noce_can_store_speculate_p (test_bb, orig_x))
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return FALSE;
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}
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/* We want to avoid store speculation to avoid cases like
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if (pthread_mutex_trylock(mutex))
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++global_variable;
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Rather than go to much effort here, we rely on the SSA optimizers,
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which do a good enough job these days. */
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return FALSE;
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if (noce_try_move (if_info))
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goto success;
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@ -3657,7 +3657,6 @@ extern void init_alias_analysis (void);
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extern void end_alias_analysis (void);
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extern void vt_equate_reg_base_value (const_rtx, const_rtx);
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extern bool memory_modified_in_insn_p (const_rtx, const_rtx);
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extern bool memory_must_be_modified_in_insn_p (const_rtx, const_rtx);
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extern bool may_be_sp_based_p (rtx);
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extern rtx gen_hard_reg_clobber (machine_mode, unsigned int);
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extern rtx get_reg_known_value (unsigned int);
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