diff --git a/src/amd/common/ac_shader_args.c b/src/amd/common/ac_shader_args.c
index 6246347972e..5f4cb6ea3e4 100644
--- a/src/amd/common/ac_shader_args.c
+++ b/src/amd/common/ac_shader_args.c
@@ -82,3 +82,35 @@ void ac_compact_ps_vgpr_args(struct ac_shader_args *info, uint32_t spi_ps_input)
 
    info->num_vgprs_used = vgpr_reg;
 }
+
+unsigned
+ac_get_color_interp_arg(const struct ac_shader_args *args, enum ac_color_interp interp)
+{
+   struct ac_arg arg;
+
+   switch (interp) {
+   case AC_COLOR_INTERP_PERSP_SAMPLE:
+      arg = args->persp_sample;
+      break;
+   case AC_COLOR_INTERP_PERSP_CENTER:
+      arg = args->persp_center;
+      break;
+   case AC_COLOR_INTERP_PERSP_CENTROID:
+      arg = args->persp_centroid;
+      break;
+   case AC_COLOR_INTERP_LINEAR_SAMPLE:
+      arg = args->linear_sample;
+      break;
+   case AC_COLOR_INTERP_LINEAR_CENTER:
+      arg = args->linear_center;
+      break;
+   case AC_COLOR_INTERP_LINEAR_CENTROID:
+      arg = args->linear_centroid;
+      break;
+   default:
+      UNREACHABLE("unexpected interp mode");
+   }
+
+   assert(arg.used);
+   return arg.arg_index;
+}
diff --git a/src/amd/common/ac_shader_args.h b/src/amd/common/ac_shader_args.h
index 64675c03854..fc47f92135f 100644
--- a/src/amd/common/ac_shader_args.h
+++ b/src/amd/common/ac_shader_args.h
@@ -10,6 +10,10 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* Maximum dwords of inline push constants when the indirect path is still used */
 #define AC_MAX_INLINE_PUSH_CONSTS_WITH_INDIRECT 8
 /* Maximum dwords of inline push constants when the indirect path is not used */
@@ -27,6 +31,16 @@ enum ac_arg_type
    AC_ARG_CONST_ADDR,
 };
 
+enum ac_color_interp {
+   AC_COLOR_INTERP_FLAT,
+   AC_COLOR_INTERP_PERSP_SAMPLE,
+   AC_COLOR_INTERP_PERSP_CENTER,
+   AC_COLOR_INTERP_PERSP_CENTROID,
+   AC_COLOR_INTERP_LINEAR_SAMPLE,
+   AC_COLOR_INTERP_LINEAR_CENTER,
+   AC_COLOR_INTERP_LINEAR_CENTROID,
+};
+
 struct ac_arg {
    uint16_t arg_index;
    bool used;
@@ -204,5 +218,10 @@ void ac_add_arg(struct ac_shader_args *info, enum ac_arg_regfile regfile, unsign
 void ac_add_return(struct ac_shader_args *info, enum ac_arg_regfile regfile);
 void ac_add_preserved(struct ac_shader_args *info, const struct ac_arg *arg);
 void ac_compact_ps_vgpr_args(struct ac_shader_args *info, uint32_t spi_ps_input);
+unsigned ac_get_color_interp_arg(const struct ac_shader_args *args, enum ac_color_interp interp);
+
+#ifdef __cplusplus
+}
+#endif
 
 #endif
diff --git a/src/amd/compiler/aco_shader_info.h b/src/amd/compiler/aco_shader_info.h
index 56f230b63b6..1b49f38134b 100644
--- a/src/amd/compiler/aco_shader_info.h
+++ b/src/amd/compiler/aco_shader_info.h
@@ -98,8 +98,8 @@ struct aco_ps_prolog_info {
    bool force_samplemask_to_helper_invocation;
    unsigned num_interp_inputs;
    unsigned colors_read;
-   int color_interp_vgpr_index[2];
-   int color_attr_index[2];
+   uint8_t color_attr_index[2];
+   enum ac_color_interp color_interp[2];
    bool color_two_side;
    bool needs_wqm;
 
diff --git a/src/amd/compiler/instruction_selection/aco_select_ps_prolog.cpp b/src/amd/compiler/instruction_selection/aco_select_ps_prolog.cpp
index 927df3c8eca..77808479a71 100644
--- a/src/amd/compiler/instruction_selection/aco_select_ps_prolog.cpp
+++ b/src/amd/compiler/instruction_selection/aco_select_ps_prolog.cpp
@@ -205,7 +205,7 @@ passthrough_all_args(isel_context* ctx, std::vector<Operand>& regs)
 }
 
 Temp
-get_interp_color(isel_context* ctx, int interp_vgpr, unsigned attr_index, unsigned comp)
+get_interp_color(isel_context* ctx, int interp_arg, unsigned attr_index, unsigned comp)
 {
    Builder bld(ctx->program, ctx->block);
 
@@ -213,10 +213,8 @@ get_interp_color(isel_context* ctx, int interp_vgpr, unsigned attr_index, unsign
 
    Temp prim_mask = get_arg(ctx, ctx->args->prim_mask);
 
-   if (interp_vgpr != -1) {
-      /* interp args are all 2 vgprs */
-      int arg_index = ctx->args->persp_sample.arg_index + interp_vgpr / 2;
-      Temp interp_ij = ctx->arg_temps[arg_index];
+   if (interp_arg != -1) {
+      Temp interp_ij = ctx->arg_temps[interp_arg];
 
       emit_interp_instr(ctx, attr_index, comp, interp_ij, dst, prim_mask, false);
    } else {
@@ -245,7 +243,9 @@ interpolate_color_args(isel_context* ctx, const struct aco_ps_prolog_info* finfo
       u_foreach_bit (i, finfo->colors_read) {
          unsigned color_index = i / 4;
          unsigned front_index = finfo->color_attr_index[color_index];
-         int interp_vgpr = finfo->color_interp_vgpr_index[color_index];
+         int interp_arg = finfo->color_interp[color_index] == AC_COLOR_INTERP_FLAT
+                             ? -1
+                             : ac_get_color_interp_arg(ctx->args, finfo->color_interp[color_index]);
 
          /* If BCOLOR0 is used, BCOLOR1 is at offset "num_inputs + 1",
           * otherwise it's at offset "num_inputs".
@@ -254,8 +254,8 @@ interpolate_color_args(isel_context* ctx, const struct aco_ps_prolog_info* finfo
          if (color_index == 1 && finfo->colors_read & 0xf)
             back_index++;
 
-         Temp front = get_interp_color(ctx, interp_vgpr, front_index, i % 4);
-         Temp back = get_interp_color(ctx, interp_vgpr, back_index, i % 4);
+         Temp front = get_interp_color(ctx, interp_arg, front_index, i % 4);
+         Temp back = get_interp_color(ctx, interp_arg, back_index, i % 4);
 
          Temp color =
             bld.vop2(aco_opcode::v_cndmask_b32, bld.def(v1), back, front, is_face_positive);
@@ -266,8 +266,10 @@ interpolate_color_args(isel_context* ctx, const struct aco_ps_prolog_info* finfo
       u_foreach_bit (i, finfo->colors_read) {
          unsigned color_index = i / 4;
          unsigned attr_index = finfo->color_attr_index[color_index];
-         int interp_vgpr = finfo->color_interp_vgpr_index[color_index];
-         Temp color = get_interp_color(ctx, interp_vgpr, attr_index, i % 4);
+         int interp_arg = finfo->color_interp[color_index] == AC_COLOR_INTERP_FLAT
+                             ? -1
+                             : ac_get_color_interp_arg(ctx->args, finfo->color_interp[color_index]);
+         Temp color = get_interp_color(ctx, interp_arg, attr_index, i % 4);
 
          regs.emplace_back(Operand(color, PhysReg{vgpr++}));
       }
diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
index f3e8e1ac95c..c9e3bee389d 100644
--- a/src/gallium/drivers/radeonsi/si_shader.c
+++ b/src/gallium/drivers/radeonsi/si_shader.c
@@ -1778,7 +1778,7 @@ static void si_get_ps_prolog_key(struct si_shader *shader, union si_shader_part_
 
          switch (interp) {
          case INTERP_MODE_FLAT:
-            key->ps_prolog.color_interp_vgpr_index[i] = -1;
+            key->ps_prolog.color_interp[i] = AC_COLOR_INTERP_FLAT;
             break;
          case INTERP_MODE_SMOOTH:
          case INTERP_MODE_COLOR:
@@ -1790,15 +1790,15 @@ static void si_get_ps_prolog_key(struct si_shader *shader, union si_shader_part_
 
             switch (location) {
             case TGSI_INTERPOLATE_LOC_SAMPLE:
-               key->ps_prolog.color_interp_vgpr_index[i] = 0;
+               key->ps_prolog.color_interp[i] = AC_COLOR_INTERP_PERSP_SAMPLE;
                shader->config.spi_ps_input_ena |= S_0286CC_PERSP_SAMPLE_ENA(1);
                break;
             case TGSI_INTERPOLATE_LOC_CENTER:
-               key->ps_prolog.color_interp_vgpr_index[i] = 2;
+               key->ps_prolog.color_interp[i] = AC_COLOR_INTERP_PERSP_CENTER;
                shader->config.spi_ps_input_ena |= S_0286CC_PERSP_CENTER_ENA(1);
                break;
             case TGSI_INTERPOLATE_LOC_CENTROID:
-               key->ps_prolog.color_interp_vgpr_index[i] = 4;
+               key->ps_prolog.color_interp[i] = AC_COLOR_INTERP_PERSP_CENTROID;
                shader->config.spi_ps_input_ena |= S_0286CC_PERSP_CENTROID_ENA(1);
                break;
             default:
@@ -1818,15 +1818,15 @@ static void si_get_ps_prolog_key(struct si_shader *shader, union si_shader_part_
              */
             switch (location) {
             case TGSI_INTERPOLATE_LOC_SAMPLE:
-               key->ps_prolog.color_interp_vgpr_index[i] = 6;
+               key->ps_prolog.color_interp[i] = AC_COLOR_INTERP_LINEAR_SAMPLE;
                shader->config.spi_ps_input_ena |= S_0286CC_LINEAR_SAMPLE_ENA(1);
                break;
             case TGSI_INTERPOLATE_LOC_CENTER:
-               key->ps_prolog.color_interp_vgpr_index[i] = 8;
+               key->ps_prolog.color_interp[i] = AC_COLOR_INTERP_LINEAR_CENTER;
                shader->config.spi_ps_input_ena |= S_0286CC_LINEAR_CENTER_ENA(1);
                break;
             case TGSI_INTERPOLATE_LOC_CENTROID:
-               key->ps_prolog.color_interp_vgpr_index[i] = 10;
+               key->ps_prolog.color_interp[i] = AC_COLOR_INTERP_LINEAR_CENTROID;
                shader->config.spi_ps_input_ena |= S_0286CC_LINEAR_CENTROID_ENA(1);
                break;
             default:
diff --git a/src/gallium/drivers/radeonsi/si_shader.h b/src/gallium/drivers/radeonsi/si_shader.h
index d1ce5850466..f1c4241b053 100644
--- a/src/gallium/drivers/radeonsi/si_shader.h
+++ b/src/gallium/drivers/radeonsi/si_shader.h
@@ -568,8 +568,8 @@ union si_shader_part_key {
       unsigned fragcoord_usage_mask : 4;
       unsigned pixel_center_integer : 1;
       unsigned wqm : 1;
-      char color_attr_index[2];
-      signed char color_interp_vgpr_index[2]; /* -1 == constant */
+      uint8_t color_attr_index[2];
+      uint8_t color_interp[2]; /* AC_COLOR_INTERP_* */
    } ps_prolog;
    struct {
       struct si_ps_epilog_bits states;
diff --git a/src/gallium/drivers/radeonsi/si_shader_aco.c b/src/gallium/drivers/radeonsi/si_shader_aco.c
index 942cd76a18d..bddc2d84cb6 100644
--- a/src/gallium/drivers/radeonsi/si_shader_aco.c
+++ b/src/gallium/drivers/radeonsi/si_shader_aco.c
@@ -260,8 +260,8 @@ si_aco_build_ps_prolog(struct aco_compiler_options *options,
       .force_samplemask_to_helper_invocation = key->ps_prolog.states.force_samplemask_to_helper_invocation,
       .num_interp_inputs = key->ps_prolog.num_interp_inputs,
       .colors_read = key->ps_prolog.colors_read,
-      .color_interp_vgpr_index[0] = key->ps_prolog.color_interp_vgpr_index[0],
-      .color_interp_vgpr_index[1] = key->ps_prolog.color_interp_vgpr_index[1],
+      .color_interp[0] = key->ps_prolog.color_interp[0],
+      .color_interp[1] = key->ps_prolog.color_interp[1],
       .color_attr_index[0] = key->ps_prolog.color_attr_index[0],
       .color_attr_index[1] = key->ps_prolog.color_attr_index[1],
       .color_two_side = key->ps_prolog.states.color_two_side,
diff --git a/src/gallium/drivers/radeonsi/si_shader_llvm_ps.c b/src/gallium/drivers/radeonsi/si_shader_llvm_ps.c
index 3d4625fda7a..3b992357df0 100644
--- a/src/gallium/drivers/radeonsi/si_shader_llvm_ps.c
+++ b/src/gallium/drivers/radeonsi/si_shader_llvm_ps.c
@@ -597,11 +597,12 @@ void si_llvm_build_ps_prolog(struct si_shader_context *ctx, union si_shader_part
       if (!writemask)
          continue;
 
-      /* If the interpolation qualifier is not CONSTANT (-1). */
       LLVMValueRef interp_ij = NULL;
-      if (key->ps_prolog.color_interp_vgpr_index[i] != -1) {
-         unsigned index =
-            args->ac.num_sgprs_used + key->ps_prolog.color_interp_vgpr_index[i];
+
+      if (key->ps_prolog.color_interp[i] != AC_COLOR_INTERP_FLAT) {
+         unsigned index = ac_get_color_interp_arg(&args->ac, key->ps_prolog.color_interp[i]);
+
+         index = args->ac.num_sgprs_used + args->ac.args[index].offset;
 
          /* Get the (i,j) updated by bc_optimize handling. */
          LLVMValueRef interp[2] = {