From 402e437a4aaf2d0fe551962d1d996e32dfcb5eb8 Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <jolesen@mozilla.com>
Date: Mon, 8 May 2017 13:57:39 -0700
Subject: [PATCH] Also return live-through values from process_inst().

The coloring algorithm will need to look at the live-through values to
check if they interfere with fixed-register outputs for calls etc.
---
 lib/cretonne/src/regalloc/coloring.rs         |  2 +-
 .../src/regalloc/live_value_tracker.rs        | 21 +++++++++++++------
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/lib/cretonne/src/regalloc/coloring.rs b/lib/cretonne/src/regalloc/coloring.rs
index a1b3899577..f664c43c48 100644
--- a/lib/cretonne/src/regalloc/coloring.rs
+++ b/lib/cretonne/src/regalloc/coloring.rs
@@ -276,7 +276,7 @@ impl<'a> Context<'a> {
                   locations: &mut EntityMap<Value, ValueLoc>) {
         // First update the live value tracker with this instruction.
         // Get lists of values that are killed and defined by `inst`.
-        let (kills, defs) = tracker.process_inst(inst, dfg, self.liveness);
+        let (_throughs, kills, defs) = tracker.process_inst(inst, dfg, self.liveness);
 
         // Get the operand constraints for `inst` that we are trying to satisfy.
         let constraints = self.encinfo
diff --git a/lib/cretonne/src/regalloc/live_value_tracker.rs b/lib/cretonne/src/regalloc/live_value_tracker.rs
index 78085564f7..4ef7df8d3a 100644
--- a/lib/cretonne/src/regalloc/live_value_tracker.rs
+++ b/lib/cretonne/src/regalloc/live_value_tracker.rs
@@ -139,7 +139,7 @@ impl LiveValueTracker {
     /// This depends on the stored live value set at `ebb`'s immediate dominator, so that must have
     /// been visited first.
     ///
-    /// Returns `(liveins, args)` as a pair or slices. The first slice is the set of live-in values
+    /// Returns `(liveins, args)` as a pair of slices. The first slice is the set of live-in values
     /// from the immediate dominator. The second slice is the set of `ebb` arguments that are live.
     /// Dead arguments with no uses are ignored and not added to the set.
     pub fn ebb_top<PO: ProgramOrder>(&mut self,
@@ -209,9 +209,16 @@ impl LiveValueTracker {
     /// Determine the set of already live values that are killed by `inst`, and add the new defined
     /// values to the tracked set.
     ///
-    /// Returns `(kills, defs)` as a pair of slices. The `defs` slice is guaranteed to be in the
-    /// same order as `inst`'s results, and includes dead defines. The order of `kills` is
-    /// arbitrary.
+    /// Returns `(throughs, kills, defs)` as a tuple of slices:
+    ///
+    /// 1. The `throughs` slice is the set of live-through values that are neither defined nor
+    ///    killed by the instruction.
+    /// 2. The `kills` slice is the set of values that were live before the instruction and are
+    ///    killed at the instruction. This does not include dead defs.
+    /// 3. The `defs` slice is guaranteed to be in the same order as `inst`'s results, and includes
+    ///    dead defines.
+    ///
+    /// The order of `throughs` and `kills` is arbitrary.
     ///
     /// The `drop_dead()` method must be called next to actually remove the dead values from the
     /// tracked set after the two returned slices are no longer needed.
@@ -219,7 +226,7 @@ impl LiveValueTracker {
                         inst: Inst,
                         dfg: &DataFlowGraph,
                         liveness: &Liveness)
-                        -> (&[LiveValue], &[LiveValue]) {
+                        -> (&[LiveValue], &[LiveValue], &[LiveValue]) {
         // Save a copy of the live values before any branches or jumps that could be somebody's
         // immediate dominator.
         match dfg[inst].analyze_branch(&dfg.value_lists) {
@@ -249,7 +256,9 @@ impl LiveValueTracker {
             }
         }
 
-        (&self.live.values[first_kill..first_def], &self.live.values[first_def..])
+        (&self.live.values[0..first_kill],
+         &self.live.values[first_kill..first_def],
+         &self.live.values[first_def..])
     }
 
     /// Drop the values that are now dead after moving past `inst`.