Mesa (master): freedreno/ir3: eliminate unnecessary absneg's

[Rob Clark]

Module: Mesa
Branch: master
Commit: f9cdbf44054009122fcc16c887fb90ccc33b52c9
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f9cdbf44054009122fcc16c887fb90ccc33b52c9

Author: Rob Clark <robclark at freedesktop.org>
Date:   Tue Apr  5 12:39:47 2016 -0400

freedreno/ir3: eliminate unnecessary absneg's

The frontend inserts (abs) and (neg)'s to convert between NIR boolean
(~0/0) and native boolean (1/0).  So we'd end up with things like:

   cmps.s.ge r1.x, ...
   absneg.s r1.x, (neg)r1.x
   absneg.s r1.x, (abs)r1.x
   sel.b32 r2.x, r0.x, r1.x, r0.y

The (neg) already gets collapsed due to the following (abs).  Now by
realizing that r1.x comes from a cmps.s instruction, we can drop the
(abs) as well.

Signed-off-by: Rob Clark <robclark at freedesktop.org>

---

 src/gallium/drivers/freedreno/ir3/ir3.h    | 12 ++++++++++++
 src/gallium/drivers/freedreno/ir3/ir3_cp.c | 17 ++++++++++++++---
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/gallium/drivers/freedreno/ir3/ir3.h b/src/gallium/drivers/freedreno/ir3/ir3.h
index 23e43b1..3859f6a 100644
--- a/src/gallium/drivers/freedreno/ir3/ir3.h
+++ b/src/gallium/drivers/freedreno/ir3/ir3.h
@@ -628,6 +628,18 @@ static inline bool is_input(struct ir3_instruction *instr)
 	}
 }
 
+static inline bool is_bool(struct ir3_instruction *instr)
+{
+	switch (instr->opc) {
+	case OPC_CMPS_F:
+	case OPC_CMPS_S:
+	case OPC_CMPS_U:
+		return true;
+	default:
+		return false;
+	}
+}
+
 static inline bool is_meta(struct ir3_instruction *instr)
 {
 	/* TODO how should we count PHI (and maybe fan-in/out) which
diff --git a/src/gallium/drivers/freedreno/ir3/ir3_cp.c b/src/gallium/drivers/freedreno/ir3/ir3_cp.c
index f032f0b..6037bec 100644
--- a/src/gallium/drivers/freedreno/ir3/ir3_cp.c
+++ b/src/gallium/drivers/freedreno/ir3/ir3_cp.c
@@ -189,8 +189,10 @@ static bool valid_flags(struct ir3_instruction *instr, unsigned n,
 /* propagate register flags from src to dst.. negates need special
  * handling to cancel each other out.
  */
-static void combine_flags(unsigned *dstflags, unsigned srcflags)
+static void combine_flags(unsigned *dstflags, struct ir3_instruction *src)
 {
+	unsigned srcflags = src->regs[1]->flags;
+
 	/* if what we are combining into already has (abs) flags,
 	 * we can drop (neg) from src:
 	 */
@@ -216,6 +218,15 @@ static void combine_flags(unsigned *dstflags, unsigned srcflags)
 	*dstflags |= srcflags & IR3_REG_IMMED;
 	*dstflags |= srcflags & IR3_REG_RELATIV;
 	*dstflags |= srcflags & IR3_REG_ARRAY;
+
+	/* if src of the src is boolean we can drop the (abs) since we know
+	 * the source value is already a postitive integer.  This cleans
+	 * up the absnegs that get inserted when converting between nir and
+	 * native boolean (see ir3_b2n/n2b)
+	 */
+	struct ir3_instruction *srcsrc = ssa(src->regs[1]);
+	if (srcsrc && is_bool(srcsrc))
+		*dstflags &= ~IR3_REG_SABS;
 }
 
 /**
@@ -241,7 +252,7 @@ reg_cp(struct ir3_instruction *instr, struct ir3_register *reg, unsigned n)
 		struct ir3_register *src_reg = src->regs[1];
 		unsigned new_flags = reg->flags;
 
-		combine_flags(&new_flags, src_reg->flags);
+		combine_flags(&new_flags, src);
 
 		if (valid_flags(instr, n, new_flags)) {
 			if (new_flags & IR3_REG_ARRAY) {
@@ -262,7 +273,7 @@ reg_cp(struct ir3_instruction *instr, struct ir3_register *reg, unsigned n)
 		struct ir3_register *src_reg = src->regs[1];
 		unsigned new_flags = reg->flags;
 
-		combine_flags(&new_flags, src_reg->flags);
+		combine_flags(&new_flags, src);
 
 		if (!valid_flags(instr, n, new_flags)) {
 			/* special case for "normal" mad instructions, we can