From 21e6a055c125022d1a10a6d57f5910cef5d2cb6d Mon Sep 17 00:00:00 2001 From: Todd Neal Date: Sat, 29 Aug 2015 12:51:04 -0500 Subject: [PATCH] [dev.ssa] cmd/compile: schedule values dependent on the control later To reduce the number of spills, give any non-phi values whose argument is the control the same priority as the control. With mask.bash, this reduces regenerated flags from 603 to 240. Change-Id: I26883d69e80357c56b343428fb528102b3f26e7a Reviewed-on: https://go-review.googlesource.com/14042 Reviewed-by: Keith Randall --- src/cmd/compile/internal/ssa/schedule.go | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/src/cmd/compile/internal/ssa/schedule.go b/src/cmd/compile/internal/ssa/schedule.go index de0b4acbf4..cf5f872e0f 100644 --- a/src/cmd/compile/internal/ssa/schedule.go +++ b/src/cmd/compile/internal/ssa/schedule.go @@ -89,9 +89,21 @@ func schedule(f *Func) { // Force the control value to be scheduled at the end, // unless it is a phi value (which must be first). score[b.Control.ID] = 4 - // TODO: some times control values are used by other values - // in the block. So the control value will not appear at - // the very end. Decide if this is a problem or not. + + // Schedule values dependent on the control value at the end. + // This reduces the number of register spills. We don't find + // all values that depend on the control, just values with a + // direct dependency. This is cheaper and in testing there + // was no difference in the number of spills. + for _, v := range b.Values { + if v.Op != OpPhi { + for _, a := range v.Args { + if a == b.Control { + score[v.ID] = 4 + } + } + } + } } // Initialize priority queue with schedulable values.