Mesa (master): i965: Avoid applying negate to wrong MAD source.

[Matt Turner]

Module: Mesa
Branch: master
Commit: d528907fd2950c7bb968fff66dd79863cd128890
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=d528907fd2950c7bb968fff66dd79863cd128890

Author: Matt Turner <mattst88 at gmail.com>
Date:   Fri Feb 27 10:59:17 2015 -0800

i965: Avoid applying negate to wrong MAD source.

For some given GLSL IR like (+ (neg x) (* 1.2 x)), the try_emit_mad
function would see that one of the +'s sources was a negate expression
and set mul_negate = true without confirming that it was actually a
multiply.

Cc: 10.5 <mesa-stable at lists.freedesktop.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89315
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89095
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

---

 src/mesa/drivers/dri/i965/brw_fs_visitor.cpp   |   28 +++++++++++-------------
 src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp |   28 +++++++++++-------------
 2 files changed, 26 insertions(+), 30 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index 7a697e8..0eab053 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -430,21 +430,16 @@ fs_visitor::try_emit_mad(ir_expression *ir)
    if (ir->type != glsl_type::float_type)
       return false;
 
-   ir_rvalue *nonmul = ir->operands[1];
-   ir_expression *mul = ir->operands[0]->as_expression();
+   ir_rvalue *nonmul;
+   ir_expression *mul;
+   bool mul_negate, mul_abs;
 
-   bool mul_negate = false, mul_abs = false;
-   if (mul && mul->operation == ir_unop_abs) {
-      mul = mul->operands[0]->as_expression();
-      mul_abs = true;
-   } else if (mul && mul->operation == ir_unop_neg) {
-      mul = mul->operands[0]->as_expression();
-      mul_negate = true;
-   }
+   for (int i = 0; i < 2; i++) {
+      mul_negate = false;
+      mul_abs = false;
 
-   if (!mul || mul->operation != ir_binop_mul) {
-      nonmul = ir->operands[0];
-      mul = ir->operands[1]->as_expression();
+      mul = ir->operands[i]->as_expression();
+      nonmul = ir->operands[1 - i];
 
       if (mul && mul->operation == ir_unop_abs) {
          mul = mul->operands[0]->as_expression();
@@ -454,10 +449,13 @@ fs_visitor::try_emit_mad(ir_expression *ir)
          mul_negate = true;
       }
 
-      if (!mul || mul->operation != ir_binop_mul)
-         return false;
+      if (mul && mul->operation == ir_binop_mul)
+         break;
    }
 
+   if (!mul || mul->operation != ir_binop_mul)
+      return false;
+
    nonmul->accept(this);
    fs_reg src0 = this->result;
 
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index 0e30772..c174fdb 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -1159,21 +1159,16 @@ vec4_visitor::try_emit_mad(ir_expression *ir)
    if (ir->type->base_type != GLSL_TYPE_FLOAT)
       return false;
 
-   ir_rvalue *nonmul = ir->operands[1];
-   ir_expression *mul = ir->operands[0]->as_expression();
+   ir_rvalue *nonmul;
+   ir_expression *mul;
+   bool mul_negate, mul_abs;
 
-   bool mul_negate = false, mul_abs = false;
-   if (mul && mul->operation == ir_unop_abs) {
-      mul = mul->operands[0]->as_expression();
-      mul_abs = true;
-   } else if (mul && mul->operation == ir_unop_neg) {
-      mul = mul->operands[0]->as_expression();
-      mul_negate = true;
-   }
+   for (int i = 0; i < 2; i++) {
+      mul_negate = false;
+      mul_abs = false;
 
-   if (!mul || mul->operation != ir_binop_mul) {
-      nonmul = ir->operands[0];
-      mul = ir->operands[1]->as_expression();
+      mul = ir->operands[i]->as_expression();
+      nonmul = ir->operands[1 - i];
 
       if (mul && mul->operation == ir_unop_abs) {
          mul = mul->operands[0]->as_expression();
@@ -1183,10 +1178,13 @@ vec4_visitor::try_emit_mad(ir_expression *ir)
          mul_negate = true;
       }
 
-      if (!mul || mul->operation != ir_binop_mul)
-         return false;
+      if (mul && mul->operation == ir_binop_mul)
+         break;
    }
 
+   if (!mul || mul->operation != ir_binop_mul)
+      return false;
+
    nonmul->accept(this);
    src_reg src0 = fix_3src_operand(this->result);