[Mesa-dev] [PATCH] ac/nir: Correctly handle imod with different signs.

[Bas Nieuwenhuizen]

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102032
---
 src/amd/common/ac_nir_to_llvm.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index 8ae8650a7b..4f1e4af37b 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -1671,6 +1671,23 @@ static LLVMValueRef emit_ddxy_interp(
        return ac_build_gather_values(&ctx->ac, result, 4);
 }
 
+static LLVMValueRef emit_imod(struct ac_llvm_context *ctx, LLVMValueRef src0, 
LLVMValueRef src1)
+{
+       /* The imod result should have the same sign as src1 when not 0. */
+
+       LLVMValueRef result = LLVMBuildSRem(ctx->builder, src0, src1, "");
+
+       LLVMValueRef diff_sign = LLVMBuildXor(ctx->builder, result, src1, "");
+       diff_sign = LLVMBuildICmp(ctx->builder, LLVMIntSLT, diff_sign, 
ctx->i32_0, "");
+
+       LLVMValueRef nonzero = LLVMBuildICmp(ctx->builder, LLVMIntNE, result, 
ctx->i32_0, "");
+
+       LLVMValueRef cond = LLVMBuildAnd(ctx->builder, diff_sign, nonzero, "");
+       LLVMValueRef offset = LLVMBuildSelect(ctx->builder, cond, src1, 
ctx->i32_0, "");
+
+       return LLVMBuildAdd(ctx->builder, result, offset, "");
+}
+
 static void visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
 {
        LLVMValueRef src[4], result = NULL;
@@ -1733,7 +1750,7 @@ static void visit_alu(struct ac_nir_context *ctx, const 
nir_alu_instr *instr)
                result = LLVMBuildMul(ctx->ac.builder, src[0], src[1], "");
                break;
        case nir_op_imod:
-               result = LLVMBuildSRem(ctx->ac.builder, src[0], src[1], "");
+               result = emit_imod(&ctx->ac, src[0], src[1]);
                break;
        case nir_op_umod:
                result = LLVMBuildURem(ctx->ac.builder, src[0], src[1], "");
-- 
2.16.1

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