[Mesa-dev] [PATCH 1/4] gallivm: fix unsigned divide and remainder opcodes

[Zack Rusin]

We want to both make sure we never divide by zero to not generate
sigfpe and that divide by zero is guaranteed to return 0xffffffff.
Based on José idea.

Signed-off-by: Zack Rusin <zackr at vmware.com>
---
 src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c |   29 +++++++++++++++++---
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c b/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
index f3ae7b6..f72fafd 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
@@ -1543,8 +1543,19 @@ udiv_emit_cpu(
    struct lp_build_tgsi_context * bld_base,
    struct lp_build_emit_data * emit_data)
 {
-   emit_data->output[emit_data->chan] = lp_build_div(&bld_base->uint_bld,
-                                   emit_data->args[0], emit_data->args[1]);
+   
+   LLVMBuilderRef builder = bld_base->base.gallivm->builder;
+   LLVMValueRef div_mask = lp_build_cmp(&bld_base->uint_bld,
+                                        PIPE_FUNC_EQUAL, emit_data->args[1],
+                                        bld_base->uint_bld.zero);
+   LLVMValueRef divisor = LLVMBuildOr(builder,
+                                      div_mask,
+                                      emit_data->args[1], "");
+   LLVMValueRef result = lp_build_div(&bld_base->uint_bld,
+                                      emit_data->args[0], divisor);
+   emit_data->output[emit_data->chan] = LLVMBuildOr(builder,
+                                                    div_mask,
+                                                    result, "");
 }
 
 /* TGSI_OPCODE_UMAX (CPU Only) */
@@ -1576,8 +1587,18 @@ umod_emit_cpu(
    struct lp_build_tgsi_context * bld_base,
    struct lp_build_emit_data * emit_data)
 {
-   emit_data->output[emit_data->chan] = lp_build_mod(&bld_base->uint_bld,
-                                   emit_data->args[0], emit_data->args[1]);
+   LLVMBuilderRef builder = bld_base->base.gallivm->builder;
+   LLVMValueRef div_mask = lp_build_cmp(&bld_base->uint_bld,
+                                        PIPE_FUNC_EQUAL, emit_data->args[1],
+                                        bld_base->uint_bld.zero);
+   LLVMValueRef divisor = LLVMBuildOr(builder,
+                                      div_mask,
+                                      emit_data->args[1], "");
+   LLVMValueRef result = lp_build_mod(&bld_base->uint_bld,
+                                      emit_data->args[0], divisor);
+   emit_data->output[emit_data->chan] = LLVMBuildOr(builder,
+                                                    div_mask,
+                                                    result, "");
 }
 
 /* TGSI_OPCODE_USET Helper (CPU Only) */
-- 
1.7.10.4