[Mesa-dev] [PATCH 13/22] glsl: Add ir_binop_pow to get_range

[Thomas Helland]

V2: Replace range-setting for undefined behavior with a TODO.
    Use the new IS_CONSTANT macro
--- 3< ---
Ian mentioned he was not sure what the correct behavior should be.
Optimizing based on undefined behavior is not pretty,
so remove that and instead leave a note.
---
 src/glsl/opt_minmax.cpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/glsl/opt_minmax.cpp b/src/glsl/opt_minmax.cpp
index dd13800..cca18e8 100644
--- a/src/glsl/opt_minmax.cpp
+++ b/src/glsl/opt_minmax.cpp
@@ -434,6 +434,20 @@ get_range(ir_rvalue *rval)
 
          return minmax_range(low, high);
 
+      case ir_binop_pow:
+         r0 = get_range(expr->operands[0]);
+
+         if (IS_CONSTANT(r0.low, >=, 0.0f))
+            low = new(mem_ctx) ir_constant(0.0f);
+
+         /* TODO: If operand(0) < 0 then the result is undefined according
+          * to the spec, so we can set the range to whatever we want.
+          * However, hardware probably follows SM2.0 or SM5.0 rules.
+          * Some apps may depend on this behavior. This needs investigation
+          */
+
+         return minmax_range(low, NULL);
+
       default:
          break;
       }
-- 
2.2.1