* Go patch committed: turn global "a = b; b = x' to "a = x" when possible
@ 2020-07-28 0:03 Ian Lance Taylor
0 siblings, 0 replies; only message in thread
From: Ian Lance Taylor @ 2020-07-28 0:03 UTC (permalink / raw)
To: gcc-patches, gofrontend-dev
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This patch to the Go frontend changes package-scope "a = b; b = x" to
just set "a = x". This avoids requiring an init function to
initialize the variable. This can only be done if x is a static
initializer.
The go1.15rc1 runtime package relies on this optimization. The
package has a variable "var maxSearchAddr = maxOffAddr". The
maxSearchAddr variable is used by code that runs before package
initialization is complete.
Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu. Committed
to mainline.
Ian
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2b29792a4c40cde1f5a5d0858234162258d7c1b3
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 0fa32a43489..12e48c19932 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-e86f2cb5d6b1984fde345d6ade605e377fa38c04
+8b9c7fb00ccaf1d4bcc8d581a1a4d46a35771b77
The first line of this file holds the git revision number of the last
merge done from the gofrontend repository.
diff --git a/gcc/go/gofrontend/gogo.cc b/gcc/go/gofrontend/gogo.cc
index c1021e5679c..4c8c55fcb14 100644
--- a/gcc/go/gofrontend/gogo.cc
+++ b/gcc/go/gofrontend/gogo.cc
@@ -1622,16 +1622,31 @@ Gogo::write_globals()
// The initializer is constant if it is the zero-value of the
// variable's type or if the initial value is an immutable value
// that is not copied to the heap.
- bool is_static_initializer = false;
- if (var->init() == NULL)
+ Expression* init = var->init();
+
+ // If we see "a = b; b = x", and x is a static
+ // initializer, just set a to x.
+ while (init != NULL && init->var_expression() != NULL)
+ {
+ Named_object* ino = init->var_expression()->named_object();
+ if (!ino->is_variable() || ino->package() != NULL)
+ break;
+ Expression* ino_init = ino->var_value()->init();
+ if (ino->var_value()->has_pre_init()
+ || ino_init == NULL
+ || !ino_init->is_static_initializer())
+ break;
+ init = ino_init;
+ }
+
+ bool is_static_initializer;
+ if (init == NULL)
is_static_initializer = true;
else
{
Type* var_type = var->type();
- Expression* init = var->init();
- Expression* init_cast =
- Expression::make_cast(var_type, init, var->location());
- is_static_initializer = init_cast->is_static_initializer();
+ init = Expression::make_cast(var_type, init, var->location());
+ is_static_initializer = init->is_static_initializer();
}
// Non-constant variable initializations might need to create
@@ -1650,7 +1665,15 @@ Gogo::write_globals()
}
var_init_fn = init_fndecl;
}
- Bexpression* var_binit = var->get_init(this, var_init_fn);
+
+ Bexpression* var_binit;
+ if (init == NULL)
+ var_binit = NULL;
+ else
+ {
+ Translate_context context(this, var_init_fn, NULL, NULL);
+ var_binit = init->get_backend(&context);
+ }
if (var_binit == NULL)
;
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2020-07-28 0:03 Go patch committed: turn global "a = b; b = x' to "a = x" when possible Ian Lance Taylor
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