From f0e6dacee529661393964725bed561c45405bae4 Mon Sep 17 00:00:00 2001 From: Jose Maria Casanova Crespo Date: Thu, 3 May 2018 01:38:47 +0200 Subject: [PATCH] intel/compiler: fix brw_imm_w for negative 16-bit integers 16-bit immediates need to replicate the 16-bit immediate value in both words of the 32-bit value. This needs to be careful to avoid sign-extension, which the previous implementation was not handling properly. For example, with the previous implementation, storing the value -3 would generate imm.d = 0xfffffffd due to signed integer sign extension, which is not correct. Instead, we should cast to uint16_t, which gives us the correct result: imm.ud = 0xfffdfffd. We only had a couple of cases hitting this path in the driver until now, one with value -1, which would work since all bits are one in this case, and another with value -2 in brw_clip_tri(), which would hit the aforementioned issue (this case only affects gen4 although we are not aware of whether this was causing an actual bug somewhere). v2: Make explicit uint32_t casting for left shift (Jason Ekstrand) Reviewed-by: Jason Ekstrand Cc: "18.0 18.1" --- src/intel/compiler/brw_reg.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/intel/compiler/brw_reg.h b/src/intel/compiler/brw_reg.h index dff9b970b2f..ac12ab3d2dd 100644 --- a/src/intel/compiler/brw_reg.h +++ b/src/intel/compiler/brw_reg.h @@ -705,7 +705,7 @@ static inline struct brw_reg brw_imm_w(int16_t w) { struct brw_reg imm = brw_imm_reg(BRW_REGISTER_TYPE_W); - imm.d = w | (w << 16); + imm.ud = (uint16_t)w | (uint32_t)(uint16_t)w << 16; return imm; } -- 2.30.2