Make it cheaper to test whether an SSA name is a virtual operand

virtual_operand_p handled SSA names by looking at the flags of the
underlying variable.  This seems to be a relatively common source
of cache misses, mainly because virtual_operand_p is the first thing
tested by is_gimple_reg.

This patch caches the information in the SSA name itself.  Several
flags seem to be free so the patch arbitrarily uses public_flag.

Tested on aarch64-linux-gnu and x86_64-linux-gnu.  It improves
compile time by a small (<1%) but reproducable amount on the
tests I've tried.  OK to install?

Thanks,
Richard


gcc/
	* tree-core.h (tree_base): Document the meaning of public_flag
	for SSA names.
	* tree.h (SSA_NAME_IS_VIRTUAL_OPERAND): New macro.
	(SET_SSA_NAME_VAR_OR_IDENTIFIER): Record whether the variable
	is a virtual operand.
	* gimple-expr.h (virtual_operand_p): Use SSA_NAME_IS_VIRTUAL_OPERAND.

On December 23, 2016 6:47:37 PM GMT+01:00, Richard Sandiford <richard.sandiford@arm.com> wrote:
>virtual_operand_p handled SSA names by looking at the flags of the
>underlying variable.  This seems to be a relatively common source
>of cache misses, mainly because virtual_operand_p is the first thing
>tested by is_gimple_reg.
>
>This patch caches the information in the SSA name itself.  Several
>flags seem to be free so the patch arbitrarily uses public_flag.
>
>Tested on aarch64-linux-gnu and x86_64-linux-gnu.  It improves
>compile time by a small (<1%) but reproducable amount on the
>tests I've tried.  OK to install?

OK.

Richard.

>Thanks,
>Richard
>
>
>gcc/
>	* tree-core.h (tree_base): Document the meaning of public_flag
>	for SSA names.
>	* tree.h (SSA_NAME_IS_VIRTUAL_OPERAND): New macro.
>	(SET_SSA_NAME_VAR_OR_IDENTIFIER): Record whether the variable
>	is a virtual operand.
>	* gimple-expr.h (virtual_operand_p): Use SSA_NAME_IS_VIRTUAL_OPERAND.
>
>diff --git a/gcc/gimple-expr.h b/gcc/gimple-expr.h
>index f2ccd29..faf4c53 100644
>--- a/gcc/gimple-expr.h
>+++ b/gcc/gimple-expr.h
>@@ -105,11 +105,7 @@ static inline bool
> virtual_operand_p (tree op)
> {
>   if (TREE_CODE (op) == SSA_NAME)
>-    {
>-      op = SSA_NAME_VAR (op);
>-      if (!op)
>-	return false;
>-    }
>+    return SSA_NAME_IS_VIRTUAL_OPERAND (op);
> 
>   if (TREE_CODE (op) == VAR_DECL)
>     return VAR_DECL_IS_VIRTUAL_OPERAND (op);
>diff --git a/gcc/tree-core.h b/gcc/tree-core.h
>index eec2d4f3..59d771c 100644
>--- a/gcc/tree-core.h
>+++ b/gcc/tree-core.h
>@@ -1091,6 +1091,9 @@ struct GTY(()) tree_base {
>        FALLTHROUGH_LABEL_P in
> 	   LABEL_DECL
> 
>+       SSA_NAME_IS_VIRTUAL_OPERAND in
>+	   SSA_NAME
>+
>    private_flag:
> 
>        TREE_PRIVATE in
>diff --git a/gcc/tree.h b/gcc/tree.h
>index 62cd7bb..e994e93 100644
>--- a/gcc/tree.h
>+++ b/gcc/tree.h
>@@ -1665,6 +1665,11 @@ extern void protected_set_expr_location (tree,
>location_t);
> 
> /* SSA_NAME accessors.  */
> 
>+/* Whether SSA_NAME NODE is a virtual operand.  This simply caches the
>+   information in the underlying SSA_NAME_VAR for efficiency.  */
>+#define SSA_NAME_IS_VIRTUAL_OPERAND(NODE) \
>+  SSA_NAME_CHECK (NODE)->base.public_flag
>+
> /* Returns the IDENTIFIER_NODE giving the SSA name a name or NULL_TREE
>    if there is no name associated with it.  */
> #define SSA_NAME_IDENTIFIER(NODE)				\
>@@ -1683,7 +1688,16 @@ extern void protected_set_expr_location (tree,
>location_t);
>    ? NULL_TREE : (NODE)->ssa_name.var)
> 
> #define SET_SSA_NAME_VAR_OR_IDENTIFIER(NODE,VAR) \
>-  do { SSA_NAME_CHECK (NODE)->ssa_name.var = (VAR); } while (0)
>+  do \
>+    { \
>+      tree var_ = (VAR); \
>+      SSA_NAME_CHECK (NODE)->ssa_name.var = var_; \
>+      SSA_NAME_IS_VIRTUAL_OPERAND (NODE) \
>+	= (var_ \
>+	   && TREE_CODE (var_) == VAR_DECL \
>+	   && VAR_DECL_IS_VIRTUAL_OPERAND (var_)); \
>+    } \
>+  while (0)
> 
> /* Returns the statement which defines this SSA name.  */
>#define SSA_NAME_DEF_STMT(NODE)	SSA_NAME_CHECK
>(NODE)->ssa_name.def_stmt