radeon/ac: add ac_emit_imsb helper.

We want to use a different intrinsic on newer llvm, so move this
code to a shared area.

Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/src/amd/common/ac_llvm_build.c b/src/amd/common/ac_llvm_build.c
index 20216a749470ada9be3f9a2d2be53296a2e95a80..180fd2414a5c713590b2410a03145e862d094d50 100644 (file)
--- a/src/amd/common/ac_llvm_build.c
+++ b/src/amd/common/ac_llvm_build.c
@@ -763,3 +763,27 @@ ac_emit_sendmsg(struct ac_llvm_context *ctx,
        ac_emit_llvm_intrinsic(ctx, intr_name, ctx->voidt,
                               args, 2, 0);
 }
+
+LLVMValueRef
+ac_emit_imsb(struct ac_llvm_context *ctx,
+            LLVMValueRef arg,
+            LLVMTypeRef dst_type)
+{
+       LLVMValueRef msb = ac_emit_llvm_intrinsic(ctx, "llvm.AMDGPU.flbit.i32",
+                                                 dst_type, &arg, 1,
+                                                 AC_FUNC_ATTR_READNONE);
+
+       /* The HW returns the last bit index from MSB, but NIR/TGSI wants
+        * the index from LSB. Invert it by doing "31 - msb". */
+       msb = LLVMBuildSub(ctx->builder, LLVMConstInt(ctx->i32, 31, false),
+                          msb, "");
+
+       LLVMValueRef all_ones = LLVMConstInt(ctx->i32, -1, true);
+       LLVMValueRef cond = LLVMBuildOr(ctx->builder,
+                                       LLVMBuildICmp(ctx->builder, LLVMIntEQ,
+                                                     arg, LLVMConstInt(ctx->i32, 0, 0), ""),
+                                       LLVMBuildICmp(ctx->builder, LLVMIntEQ,
+                                                     arg, all_ones, ""), "");
+
+       return LLVMBuildSelect(ctx->builder, cond, all_ones, msb, "");
+}

diff --git a/src/amd/common/ac_llvm_build.h b/src/amd/common/ac_llvm_build.h
index e88874ad46b9a3bd8c2b87b7f68a8dd68725646b..0ff04e4c703599c7b685aecbd7e2995818865a13 100644 (file)
--- a/src/amd/common/ac_llvm_build.h
+++ b/src/amd/common/ac_llvm_build.h
@@ -182,6 +182,10 @@ void ac_emit_sendmsg(struct ac_llvm_context *ctx,
                     uint32_t msg,
                     LLVMValueRef wave_id);
 
+LLVMValueRef ac_emit_imsb(struct ac_llvm_context *ctx,
+                         LLVMValueRef arg,
+                         LLVMTypeRef dst_type);
+
 #ifdef __cplusplus
 }
 #endif