Mesa (master): intel/fs: Fix D to W conversion in opt_combine_constants

[GitLab Mirror]

Module: Mesa
Branch: master
Commit: 21223acf7d5b39e5eb2b248330519cdbee3e63e8
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=21223acf7d5b39e5eb2b248330519cdbee3e63e8

Author: Ian Romanick <ian.d.romanick at intel.com>
Date:   Fri Apr 19 11:32:59 2019 -0700

intel/fs: Fix D to W conversion in opt_combine_constants

Found by GCC warning:

src/intel/compiler/brw_fs_combine_constants.cpp: In function ‘bool needs_negate(const fs_reg*, const imm*)’:
src/intel/compiler/brw_fs_combine_constants.cpp:306:34: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
       return ((reg->d & 0xffffu) < 0) != (imm->w < 0);
               ~~~~~~~~~~~~~~~~~~~^~~

The result of the bit-and is a 32-bit value with the top bits all zero.
This will never be < 0.  Instead of masking off the bits, just cast to
int16_t and let the compiler handle the actual conversion.

Fixes: e64be391dd0 ("intel/compiler: generalize the combine constants pass")
Cc: Iago Toral Quiroga <itoral at igalia.com>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

---

 src/intel/compiler/brw_fs_combine_constants.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/intel/compiler/brw_fs_combine_constants.cpp b/src/intel/compiler/brw_fs_combine_constants.cpp
index db7b14a8312..8d16be4c4bb 100644
--- a/src/intel/compiler/brw_fs_combine_constants.cpp
+++ b/src/intel/compiler/brw_fs_combine_constants.cpp
@@ -303,7 +303,7 @@ needs_negate(const struct fs_reg *reg, const struct imm *imm)
    case BRW_REGISTER_TYPE_HF:
       return (reg->d & 0x8000u) != (imm->w & 0x8000u);
    case BRW_REGISTER_TYPE_W:
-      return ((reg->d & 0xffffu) < 0) != (imm->w < 0);
+      return ((int16_t)reg->d < 0) != (imm->w < 0);
    case BRW_REGISTER_TYPE_UQ:
    case BRW_REGISTER_TYPE_UD:
    case BRW_REGISTER_TYPE_UW: