From d7614993153b4e4da323b52acf78bd4dc3cbcfa7 Mon Sep 17 00:00:00 2001
From: pcpa <paulo.cesar.pereira.de.andrade@gmail.com>
Date: Tue, 9 May 2017 13:27:37 -0400
Subject: [PATCH] Add a second pass to compute live register ranges

	* include/lightning/jit_private.h, lib/lightning.c: Add a
	second pass from start when computing register live ranges.
	This should be used temporarily, and is required for certain
	loop constructs, with several consecutive blocks not referencing
	a live register.
---
 ChangeLog                       |  8 ++++++++
 include/lightning/jit_private.h |  1 +
 lib/lightning.c                 | 17 ++++++++++++++++-
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index baf1069d1..97263f7bb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2017-06-09 Paulo Andrade <pcpa@gnu.org>
+
+	* include/lightning/jit_private.h, lib/lightning.c: Add a
+	second pass from start when computing register live ranges.
+	This should be used temporarily, and is required for certain
+	loop constructs, with several consecutive blocks not referencing
+	a live register.
+
 2016-05-05 Paulo Andrade <pcpa@gnu.org>
 
 	* lib/lightning.c: Correct wrong movr simplification,
diff --git a/include/lightning/jit_private.h b/include/lightning/jit_private.h
index 0730439cd..05db0b001 100644
--- a/include/lightning/jit_private.h
+++ b/include/lightning/jit_private.h
@@ -379,6 +379,7 @@ struct jit_block {
     jit_node_t		*label;
     jit_regset_t	 reglive;
     jit_regset_t	 regmask;
+    jit_regset_t	 setmask;	/* Used for forward second pass */
 };
 
 struct jit_value {
diff --git a/lib/lightning.c b/lib/lightning.c
index 0dfec4854..d6b033cf9 100644
--- a/lib/lightning.c
+++ b/lib/lightning.c
@@ -1560,8 +1560,10 @@ _jit_optimize(jit_state_t *_jit)
 	block = _jitc->blocks.ptr + offset;
 	if (!block->label)
 	    continue;
-	if (block->label->code != jit_code_epilog)
+	if (block->label->code != jit_code_epilog) {
 	    jit_setup(block);
+	    jit_regset_set(&block->setmask, &block->regmask);
+	}
     }
     /* call jit_update resolving undefined values in reverse
      * order so that sequential code would find most data already
@@ -1575,6 +1577,19 @@ _jit_optimize(jit_state_t *_jit)
 	    jit_update(block->label->next, &block->reglive, &_jitc->regmask);
 	}
     }
+    /* do a second pass from start to properly handle some conditions
+     * of very long living registers that are not referenced for
+     * several blocks */
+    bmp_zero();
+    for (offset = 0; offset < _jitc->blocks.offset; offset++) {
+	block = _jitc->blocks.ptr + offset;
+	if (!block->label)
+	    continue;
+	if (block->label->code != jit_code_epilog) {
+	    jit_regset_set(&_jitc->regmask, &block->setmask);
+	    jit_update(block->label->next, &block->reglive, &_jitc->regmask);
+	}
+    }
 
     patch_registers();
     simplify();