gallium: change comments to remove 'state tracker'
[mesa.git] / src / gallium / drivers / vc4 / vc4_qpu.c
index 723b36136651572f64646a36a6355d74f046ef9c..380b9f43c595cd6e55cc365cbb6092dc390524e1 100644 (file)
  */
 
 #include <stdbool.h>
+#include "util/ralloc.h"
 #include "vc4_qir.h"
 #include "vc4_qpu.h"
 
+#define QPU_MUX(mux, muxfield)                                  \
+        QPU_SET_FIELD(mux != QPU_MUX_SMALL_IMM ? mux : QPU_MUX_B, muxfield)
+
 static uint64_t
 set_src_raddr(uint64_t inst, struct qpu_reg src)
 {
         if (src.mux == QPU_MUX_A) {
                 assert(QPU_GET_FIELD(inst, QPU_RADDR_A) == QPU_R_NOP ||
                        QPU_GET_FIELD(inst, QPU_RADDR_A) == src.addr);
-                return ((inst & ~QPU_RADDR_A_MASK) |
-                        QPU_SET_FIELD(src.addr, QPU_RADDR_A));
+                return QPU_UPDATE_FIELD(inst, src.addr, QPU_RADDR_A);
         }
 
         if (src.mux == QPU_MUX_B) {
-                assert(QPU_GET_FIELD(inst, QPU_RADDR_B) == QPU_R_NOP ||
-                       QPU_GET_FIELD(inst, QPU_RADDR_B) == src.addr);
+                assert((QPU_GET_FIELD(inst, QPU_RADDR_B) == QPU_R_NOP ||
+                        QPU_GET_FIELD(inst, QPU_RADDR_B) == src.addr) &&
+                       QPU_GET_FIELD(inst, QPU_SIG) != QPU_SIG_SMALL_IMM);
+                return QPU_UPDATE_FIELD(inst, src.addr, QPU_RADDR_B);
+        }
+
+        if (src.mux == QPU_MUX_SMALL_IMM) {
+                if (QPU_GET_FIELD(inst, QPU_SIG) == QPU_SIG_SMALL_IMM) {
+                        assert(QPU_GET_FIELD(inst, QPU_RADDR_B) == src.addr);
+                } else {
+                        inst = qpu_set_sig(inst, QPU_SIG_SMALL_IMM);
+                        assert(QPU_GET_FIELD(inst, QPU_RADDR_B) == QPU_R_NOP);
+                }
                 return ((inst & ~QPU_RADDR_B_MASK) |
                         QPU_SET_FIELD(src.addr, QPU_RADDR_B));
         }
@@ -102,15 +116,15 @@ qpu_a_MOV(struct qpu_reg dst, struct qpu_reg src)
 {
         uint64_t inst = 0;
 
+        inst |= QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG);
         inst |= QPU_SET_FIELD(QPU_A_OR, QPU_OP_ADD);
         inst |= QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_A);
         inst |= QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_B);
         inst |= qpu_a_dst(dst);
         inst |= QPU_SET_FIELD(QPU_COND_ALWAYS, QPU_COND_ADD);
-        inst |= QPU_SET_FIELD(src.mux, QPU_ADD_A);
-        inst |= QPU_SET_FIELD(src.mux, QPU_ADD_B);
+        inst |= QPU_MUX(src.mux, QPU_ADD_A);
+        inst |= QPU_MUX(src.mux, QPU_ADD_B);
         inst = set_src_raddr(inst, src);
-        inst |= QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG);
         inst |= QPU_SET_FIELD(QPU_W_NOP, QPU_WADDR_MUL);
 
         return inst;
@@ -121,15 +135,15 @@ qpu_m_MOV(struct qpu_reg dst, struct qpu_reg src)
 {
         uint64_t inst = 0;
 
+        inst |= QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG);
         inst |= QPU_SET_FIELD(QPU_M_V8MIN, QPU_OP_MUL);
         inst |= QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_A);
         inst |= QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_B);
         inst |= qpu_m_dst(dst);
         inst |= QPU_SET_FIELD(QPU_COND_ALWAYS, QPU_COND_MUL);
-        inst |= QPU_SET_FIELD(src.mux, QPU_MUL_A);
-        inst |= QPU_SET_FIELD(src.mux, QPU_MUL_B);
+        inst |= QPU_MUX(src.mux, QPU_MUL_A);
+        inst |= QPU_MUX(src.mux, QPU_MUL_B);
         inst = set_src_raddr(inst, src);
-        inst |= QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG);
         inst |= QPU_SET_FIELD(QPU_W_NOP, QPU_WADDR_ADD);
 
         return inst;
@@ -150,22 +164,50 @@ qpu_load_imm_ui(struct qpu_reg dst, uint32_t val)
         return inst;
 }
 
+uint64_t
+qpu_load_imm_u2(struct qpu_reg dst, uint32_t val)
+{
+        return qpu_load_imm_ui(dst, val) | QPU_SET_FIELD(QPU_LOAD_IMM_MODE_U2,
+                                                         QPU_LOAD_IMM_MODE);
+}
+
+uint64_t
+qpu_load_imm_i2(struct qpu_reg dst, uint32_t val)
+{
+        return qpu_load_imm_ui(dst, val) | QPU_SET_FIELD(QPU_LOAD_IMM_MODE_I2,
+                                                         QPU_LOAD_IMM_MODE);
+}
+
+uint64_t
+qpu_branch(uint32_t cond, uint32_t target)
+{
+        uint64_t inst = 0;
+
+        inst |= qpu_a_dst(qpu_ra(QPU_W_NOP));
+        inst |= qpu_m_dst(qpu_rb(QPU_W_NOP));
+        inst |= QPU_SET_FIELD(cond, QPU_BRANCH_COND);
+        inst |= QPU_SET_FIELD(QPU_SIG_BRANCH, QPU_SIG);
+        inst |= QPU_SET_FIELD(target, QPU_BRANCH_TARGET);
+
+        return inst;
+}
+
 uint64_t
 qpu_a_alu2(enum qpu_op_add op,
            struct qpu_reg dst, struct qpu_reg src0, struct qpu_reg src1)
 {
         uint64_t inst = 0;
 
+        inst |= QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG);
         inst |= QPU_SET_FIELD(op, QPU_OP_ADD);
         inst |= QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_A);
         inst |= QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_B);
         inst |= qpu_a_dst(dst);
         inst |= QPU_SET_FIELD(QPU_COND_ALWAYS, QPU_COND_ADD);
-        inst |= QPU_SET_FIELD(src0.mux, QPU_ADD_A);
+        inst |= QPU_MUX(src0.mux, QPU_ADD_A);
         inst = set_src_raddr(inst, src0);
-        inst |= QPU_SET_FIELD(src1.mux, QPU_ADD_B);
+        inst |= QPU_MUX(src1.mux, QPU_ADD_B);
         inst = set_src_raddr(inst, src1);
-        inst |= QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG);
         inst |= QPU_SET_FIELD(QPU_W_NOP, QPU_WADDR_MUL);
 
         return inst;
@@ -177,72 +219,438 @@ qpu_m_alu2(enum qpu_op_mul op,
 {
         uint64_t inst = 0;
 
+        inst |= QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG);
         inst |= QPU_SET_FIELD(op, QPU_OP_MUL);
         inst |= QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_A);
         inst |= QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_B);
         inst |= qpu_m_dst(dst);
         inst |= QPU_SET_FIELD(QPU_COND_ALWAYS, QPU_COND_MUL);
-        inst |= QPU_SET_FIELD(src0.mux, QPU_MUL_A);
+        inst |= QPU_MUX(src0.mux, QPU_MUL_A);
         inst = set_src_raddr(inst, src0);
-        inst |= QPU_SET_FIELD(src1.mux, QPU_MUL_B);
+        inst |= QPU_MUX(src1.mux, QPU_MUL_B);
         inst = set_src_raddr(inst, src1);
-        inst |= QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG);
         inst |= QPU_SET_FIELD(QPU_W_NOP, QPU_WADDR_ADD);
 
         return inst;
 }
 
-static uint64_t
-merge_fields(uint64_t merge,
-             uint64_t add, uint64_t mul,
+uint64_t
+qpu_m_rot(struct qpu_reg dst, struct qpu_reg src0, int rot)
+{
+       uint64_t inst = 0;
+       inst = qpu_m_alu2(QPU_M_V8MIN, dst, src0, src0);
+
+       inst = QPU_UPDATE_FIELD(inst, QPU_SIG_SMALL_IMM, QPU_SIG);
+       inst = QPU_UPDATE_FIELD(inst, QPU_SMALL_IMM_MUL_ROT + rot,
+                                QPU_SMALL_IMM);
+
+       return inst;
+}
+
+static bool
+merge_fields(uint64_t *merge,
+             uint64_t a, uint64_t b,
              uint64_t mask, uint64_t ignore)
 {
-        if ((add & mask) == ignore)
-                return (merge & ~mask) | (mul & mask);
-        else if ((mul & mask) == ignore)
-                return (merge & ~mask) | (add & mask);
-        else {
-                assert((add & mask) == (mul & mask));
-                return merge;
+        if ((a & mask) == ignore) {
+                *merge = (*merge & ~mask) | (b & mask);
+        } else if ((b & mask) == ignore) {
+                *merge = (*merge & ~mask) | (a & mask);
+        } else {
+                if ((a & mask) != (b & mask))
+                        return false;
+        }
+
+        return true;
+}
+
+int
+qpu_num_sf_accesses(uint64_t inst)
+{
+        int accesses = 0;
+        static const uint32_t specials[] = {
+                QPU_W_TLB_COLOR_MS,
+                QPU_W_TLB_COLOR_ALL,
+                QPU_W_TLB_Z,
+                QPU_W_TMU0_S,
+                QPU_W_TMU0_T,
+                QPU_W_TMU0_R,
+                QPU_W_TMU0_B,
+                QPU_W_TMU1_S,
+                QPU_W_TMU1_T,
+                QPU_W_TMU1_R,
+                QPU_W_TMU1_B,
+                QPU_W_SFU_RECIP,
+                QPU_W_SFU_RECIPSQRT,
+                QPU_W_SFU_EXP,
+                QPU_W_SFU_LOG,
+        };
+        uint32_t waddr_add = QPU_GET_FIELD(inst, QPU_WADDR_ADD);
+        uint32_t waddr_mul = QPU_GET_FIELD(inst, QPU_WADDR_MUL);
+        uint32_t raddr_a = QPU_GET_FIELD(inst, QPU_RADDR_A);
+        uint32_t raddr_b = QPU_GET_FIELD(inst, QPU_RADDR_B);
+
+        for (int j = 0; j < ARRAY_SIZE(specials); j++) {
+                if (waddr_add == specials[j])
+                        accesses++;
+                if (waddr_mul == specials[j])
+                        accesses++;
+        }
+
+        if (raddr_a == QPU_R_MUTEX_ACQUIRE)
+                accesses++;
+        if (raddr_b == QPU_R_MUTEX_ACQUIRE &&
+            QPU_GET_FIELD(inst, QPU_SIG) != QPU_SIG_SMALL_IMM)
+                accesses++;
+
+        /* XXX: semaphore, combined color read/write? */
+        switch (QPU_GET_FIELD(inst, QPU_SIG)) {
+        case QPU_SIG_COLOR_LOAD:
+        case QPU_SIG_COLOR_LOAD_END:
+        case QPU_SIG_LOAD_TMU0:
+        case QPU_SIG_LOAD_TMU1:
+                accesses++;
         }
+
+        return accesses;
+}
+
+static bool
+qpu_waddr_ignores_ws(uint32_t waddr)
+{
+        switch(waddr) {
+        case QPU_W_ACC0:
+        case QPU_W_ACC1:
+        case QPU_W_ACC2:
+        case QPU_W_ACC3:
+        case QPU_W_NOP:
+        case QPU_W_TLB_Z:
+        case QPU_W_TLB_COLOR_MS:
+        case QPU_W_TLB_COLOR_ALL:
+        case QPU_W_TLB_ALPHA_MASK:
+        case QPU_W_VPM:
+        case QPU_W_SFU_RECIP:
+        case QPU_W_SFU_RECIPSQRT:
+        case QPU_W_SFU_EXP:
+        case QPU_W_SFU_LOG:
+        case QPU_W_TMU0_S:
+        case QPU_W_TMU0_T:
+        case QPU_W_TMU0_R:
+        case QPU_W_TMU0_B:
+        case QPU_W_TMU1_S:
+        case QPU_W_TMU1_T:
+        case QPU_W_TMU1_R:
+        case QPU_W_TMU1_B:
+                return true;
+        }
+
+        return false;
+}
+
+static void
+swap_ra_file_mux_helper(uint64_t *merge, uint64_t *a, uint32_t mux_shift)
+{
+        uint64_t mux_mask = (uint64_t)0x7 << mux_shift;
+        uint64_t mux_a_val = (uint64_t)QPU_MUX_A << mux_shift;
+        uint64_t mux_b_val = (uint64_t)QPU_MUX_B << mux_shift;
+
+        if ((*a & mux_mask) == mux_a_val) {
+                *a = (*a & ~mux_mask) | mux_b_val;
+                *merge = (*merge & ~mux_mask) | mux_b_val;
+        }
+}
+
+static bool
+try_swap_ra_file(uint64_t *merge, uint64_t *a, uint64_t *b)
+{
+        uint32_t raddr_a_a = QPU_GET_FIELD(*a, QPU_RADDR_A);
+        uint32_t raddr_a_b = QPU_GET_FIELD(*a, QPU_RADDR_B);
+        uint32_t raddr_b_a = QPU_GET_FIELD(*b, QPU_RADDR_A);
+        uint32_t raddr_b_b = QPU_GET_FIELD(*b, QPU_RADDR_B);
+
+        if (raddr_a_b != QPU_R_NOP)
+                return false;
+
+        switch (raddr_a_a) {
+        case QPU_R_UNIF:
+        case QPU_R_VARY:
+                break;
+        default:
+                return false;
+        }
+
+        if (!(*merge & QPU_PM) &&
+            QPU_GET_FIELD(*merge, QPU_UNPACK) != QPU_UNPACK_NOP) {
+                return false;
+        }
+
+        if (raddr_b_b != QPU_R_NOP &&
+            raddr_b_b != raddr_a_a)
+                return false;
+
+        /* Move raddr A to B in instruction a. */
+        *a = (*a & ~QPU_RADDR_A_MASK) | QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_A);
+        *a = (*a & ~QPU_RADDR_B_MASK) | QPU_SET_FIELD(raddr_a_a, QPU_RADDR_B);
+        *merge = QPU_UPDATE_FIELD(*merge, raddr_b_a, QPU_RADDR_A);
+        *merge = QPU_UPDATE_FIELD(*merge, raddr_a_a, QPU_RADDR_B);
+        swap_ra_file_mux_helper(merge, a, QPU_ADD_A_SHIFT);
+        swap_ra_file_mux_helper(merge, a, QPU_ADD_B_SHIFT);
+        swap_ra_file_mux_helper(merge, a, QPU_MUL_A_SHIFT);
+        swap_ra_file_mux_helper(merge, a, QPU_MUL_B_SHIFT);
+
+        return true;
+}
+
+static bool
+convert_mov(uint64_t *inst)
+{
+        uint32_t add_a = QPU_GET_FIELD(*inst, QPU_ADD_A);
+        uint32_t waddr_add = QPU_GET_FIELD(*inst, QPU_WADDR_ADD);
+        uint32_t cond_add = QPU_GET_FIELD(*inst, QPU_COND_ADD);
+
+        /* Is it a MOV? */
+        if (QPU_GET_FIELD(*inst, QPU_OP_ADD) != QPU_A_OR ||
+            (add_a != QPU_GET_FIELD(*inst, QPU_ADD_B))) {
+                return false;
+        }
+
+        if (QPU_GET_FIELD(*inst, QPU_SIG) != QPU_SIG_NONE)
+                return false;
+
+        /* We could maybe support this in the .8888 and .8a-.8d cases. */
+        if (*inst & QPU_PM)
+                return false;
+
+        *inst = QPU_UPDATE_FIELD(*inst, QPU_A_NOP, QPU_OP_ADD);
+        *inst = QPU_UPDATE_FIELD(*inst, QPU_M_V8MIN, QPU_OP_MUL);
+
+        *inst = QPU_UPDATE_FIELD(*inst, add_a, QPU_MUL_A);
+        *inst = QPU_UPDATE_FIELD(*inst, add_a, QPU_MUL_B);
+        *inst = QPU_UPDATE_FIELD(*inst, QPU_MUX_R0, QPU_ADD_A);
+        *inst = QPU_UPDATE_FIELD(*inst, QPU_MUX_R0, QPU_ADD_B);
+
+        *inst = QPU_UPDATE_FIELD(*inst, waddr_add, QPU_WADDR_MUL);
+        *inst = QPU_UPDATE_FIELD(*inst, QPU_W_NOP, QPU_WADDR_ADD);
+
+        *inst = QPU_UPDATE_FIELD(*inst, cond_add, QPU_COND_MUL);
+        *inst = QPU_UPDATE_FIELD(*inst, QPU_COND_NEVER, QPU_COND_ADD);
+
+        if (!qpu_waddr_ignores_ws(waddr_add))
+                *inst ^= QPU_WS;
+
+        return true;
+}
+
+static bool
+writes_a_file(uint64_t inst)
+{
+        if (!(inst & QPU_WS))
+                return QPU_GET_FIELD(inst, QPU_WADDR_ADD) < 32;
+        else
+                return QPU_GET_FIELD(inst, QPU_WADDR_MUL) < 32;
+}
+
+static bool
+reads_r4(uint64_t inst)
+{
+        return (QPU_GET_FIELD(inst, QPU_ADD_A) == QPU_MUX_R4 ||
+                QPU_GET_FIELD(inst, QPU_ADD_B) == QPU_MUX_R4 ||
+                QPU_GET_FIELD(inst, QPU_MUL_A) == QPU_MUX_R4 ||
+                QPU_GET_FIELD(inst, QPU_MUL_B) == QPU_MUX_R4);
 }
 
 uint64_t
-qpu_inst(uint64_t add, uint64_t mul)
+qpu_merge_inst(uint64_t a, uint64_t b)
 {
-        uint64_t merge = ((add & ~QPU_WADDR_MUL_MASK) |
-                          (mul & ~QPU_WADDR_ADD_MASK));
+        uint64_t merge = a | b;
+        bool ok = true;
+        uint32_t a_sig = QPU_GET_FIELD(a, QPU_SIG);
+        uint32_t b_sig = QPU_GET_FIELD(b, QPU_SIG);
+
+        if (QPU_GET_FIELD(a, QPU_OP_ADD) != QPU_A_NOP &&
+            QPU_GET_FIELD(b, QPU_OP_ADD) != QPU_A_NOP) {
+                if (QPU_GET_FIELD(a, QPU_OP_MUL) != QPU_M_NOP ||
+                    QPU_GET_FIELD(b, QPU_OP_MUL) != QPU_M_NOP ||
+                    !(convert_mov(&a) || convert_mov(&b))) {
+                        return 0;
+                } else {
+                        merge = a | b;
+                }
+        }
+
+        if (QPU_GET_FIELD(a, QPU_OP_MUL) != QPU_M_NOP &&
+            QPU_GET_FIELD(b, QPU_OP_MUL) != QPU_M_NOP)
+                return 0;
+
+        if (qpu_num_sf_accesses(a) && qpu_num_sf_accesses(b))
+                return 0;
+
+        if (a_sig == QPU_SIG_LOAD_IMM ||
+            b_sig == QPU_SIG_LOAD_IMM ||
+            a_sig == QPU_SIG_SMALL_IMM ||
+            b_sig == QPU_SIG_SMALL_IMM ||
+            a_sig == QPU_SIG_BRANCH ||
+            b_sig == QPU_SIG_BRANCH) {
+                return 0;
+        }
 
-        merge = merge_fields(merge, add, mul, QPU_SIG_MASK,
-                             QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG));
+        ok = ok && merge_fields(&merge, a, b, QPU_SIG_MASK,
+                                QPU_SET_FIELD(QPU_SIG_NONE, QPU_SIG));
+
+        /* Misc fields that have to match exactly. */
+        ok = ok && merge_fields(&merge, a, b, QPU_SF, ~0);
+
+        if (!merge_fields(&merge, a, b, QPU_RADDR_A_MASK,
+                          QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_A))) {
+                /* Since we tend to use regfile A by default both for register
+                 * allocation and for our special values (uniforms and
+                 * varyings), try swapping uniforms and varyings to regfile B
+                 * to resolve raddr A conflicts.
+                 */
+                if (!try_swap_ra_file(&merge, &a, &b) &&
+                    !try_swap_ra_file(&merge, &b, &a)) {
+                        return 0;
+                }
+        }
 
-        merge = merge_fields(merge, add, mul, QPU_RADDR_A_MASK,
-                             QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_A));
-        merge = merge_fields(merge, add, mul, QPU_RADDR_B_MASK,
-                             QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_B));
+        ok = ok && merge_fields(&merge, a, b, QPU_RADDR_B_MASK,
+                                QPU_SET_FIELD(QPU_R_NOP, QPU_RADDR_B));
+
+        ok = ok && merge_fields(&merge, a, b, QPU_WADDR_ADD_MASK,
+                                QPU_SET_FIELD(QPU_W_NOP, QPU_WADDR_ADD));
+        ok = ok && merge_fields(&merge, a, b, QPU_WADDR_MUL_MASK,
+                                QPU_SET_FIELD(QPU_W_NOP, QPU_WADDR_MUL));
+
+        /* Allow disagreement on WS (swapping A vs B physical reg file as the
+         * destination for ADD/MUL) if one of the original instructions
+         * ignores it (probably because it's just writing to accumulators).
+         */
+        if (qpu_waddr_ignores_ws(QPU_GET_FIELD(a, QPU_WADDR_ADD)) &&
+            qpu_waddr_ignores_ws(QPU_GET_FIELD(a, QPU_WADDR_MUL))) {
+                merge = (merge & ~QPU_WS) | (b & QPU_WS);
+        } else if (qpu_waddr_ignores_ws(QPU_GET_FIELD(b, QPU_WADDR_ADD)) &&
+                   qpu_waddr_ignores_ws(QPU_GET_FIELD(b, QPU_WADDR_MUL))) {
+                merge = (merge & ~QPU_WS) | (a & QPU_WS);
+        } else {
+                if ((a & QPU_WS) != (b & QPU_WS))
+                        return 0;
+        }
+
+        if (!merge_fields(&merge, a, b, QPU_PM, ~0)) {
+                /* If one instruction has PM bit set and the other not, the
+                 * one without PM shouldn't do packing/unpacking, and we
+                 * have to make sure non-NOP packing/unpacking from PM
+                 * instruction aren't added to it.
+                 */
+                uint64_t temp;
+
+                /* Let a be the one with PM bit */
+                if (!(a & QPU_PM)) {
+                        temp = a;
+                        a = b;
+                        b = temp;
+                }
+
+                if ((b & (QPU_PACK_MASK | QPU_UNPACK_MASK)) != 0)
+                        return 0;
+
+                if ((a & QPU_PACK_MASK) != 0 &&
+                    QPU_GET_FIELD(b, QPU_OP_MUL) != QPU_M_NOP)
+                        return 0;
+
+                if ((a & QPU_UNPACK_MASK) != 0 && reads_r4(b))
+                        return 0;
+        } else {
+                /* packing: Make sure that non-NOP packs agree, then deal with
+                 * special-case failing of adding a non-NOP pack to something
+                 * with a NOP pack.
+                 */
+                if (!merge_fields(&merge, a, b, QPU_PACK_MASK, 0))
+                        return 0;
+                bool new_a_pack = (QPU_GET_FIELD(a, QPU_PACK) !=
+                                QPU_GET_FIELD(merge, QPU_PACK));
+                bool new_b_pack = (QPU_GET_FIELD(b, QPU_PACK) !=
+                                QPU_GET_FIELD(merge, QPU_PACK));
+                if (!(merge & QPU_PM)) {
+                        /* Make sure we're not going to be putting a new
+                         * a-file packing on either half.
+                         */
+                        if (new_a_pack && writes_a_file(a))
+                                return 0;
+
+                        if (new_b_pack && writes_a_file(b))
+                                return 0;
+                } else {
+                        /* Make sure we're not going to be putting new MUL
+                         * packing oneither half.
+                         */
+                        if (new_a_pack &&
+                            QPU_GET_FIELD(a, QPU_OP_MUL) != QPU_M_NOP)
+                                return 0;
+
+                        if (new_b_pack &&
+                            QPU_GET_FIELD(b, QPU_OP_MUL) != QPU_M_NOP)
+                                return 0;
+                }
+
+                /* unpacking: Make sure that non-NOP unpacks agree, then deal
+                 * with special-case failing of adding a non-NOP unpack to
+                 * something with a NOP unpack.
+                 */
+                if (!merge_fields(&merge, a, b, QPU_UNPACK_MASK, 0))
+                        return 0;
+                bool new_a_unpack = (QPU_GET_FIELD(a, QPU_UNPACK) !=
+                                QPU_GET_FIELD(merge, QPU_UNPACK));
+                bool new_b_unpack = (QPU_GET_FIELD(b, QPU_UNPACK) !=
+                                QPU_GET_FIELD(merge, QPU_UNPACK));
+                if (!(merge & QPU_PM)) {
+                        /* Make sure we're not going to be putting a new
+                         * a-file packing on either half.
+                         */
+                        if (new_a_unpack &&
+                            QPU_GET_FIELD(a, QPU_RADDR_A) != QPU_R_NOP)
+                                return 0;
+
+                        if (new_b_unpack &&
+                            QPU_GET_FIELD(b, QPU_RADDR_A) != QPU_R_NOP)
+                                return 0;
+                } else {
+                        /* Make sure we're not going to be putting new r4
+                         * unpack on either half.
+                         */
+                        if (new_a_unpack && reads_r4(a))
+                                return 0;
+
+                        if (new_b_unpack && reads_r4(b))
+                                return 0;
+                }
+        }
 
-        return merge;
+        if (ok)
+                return merge;
+        else
+                return 0;
 }
 
 uint64_t
 qpu_set_sig(uint64_t inst, uint32_t sig)
 {
         assert(QPU_GET_FIELD(inst, QPU_SIG) == QPU_SIG_NONE);
-        return (inst & ~QPU_SIG_MASK) | QPU_SET_FIELD(sig, QPU_SIG);
+        return QPU_UPDATE_FIELD(inst, sig, QPU_SIG);
 }
 
 uint64_t
-qpu_set_cond_add(uint64_t inst, uint32_t sig)
+qpu_set_cond_add(uint64_t inst, uint32_t cond)
 {
         assert(QPU_GET_FIELD(inst, QPU_COND_ADD) == QPU_COND_ALWAYS);
-        return (inst & ~QPU_COND_ADD_MASK) | QPU_SET_FIELD(sig, QPU_COND_ADD);
+        return QPU_UPDATE_FIELD(inst, cond, QPU_COND_ADD);
 }
 
 uint64_t
-qpu_set_cond_mul(uint64_t inst, uint32_t sig)
+qpu_set_cond_mul(uint64_t inst, uint32_t cond)
 {
         assert(QPU_GET_FIELD(inst, QPU_COND_MUL) == QPU_COND_ALWAYS);
-        return (inst & ~QPU_COND_MUL_MASK) | QPU_SET_FIELD(sig, QPU_COND_MUL);
+        return QPU_UPDATE_FIELD(inst, cond, QPU_COND_MUL);
 }
 
 bool
@@ -269,13 +677,63 @@ qpu_inst_is_tlb(uint64_t inst)
                 sig == QPU_SIG_WAIT_FOR_SCOREBOARD);
 }
 
+/**
+ * Returns the small immediate value to be encoded in to the raddr b field if
+ * the argument can be represented as one, or ~0 otherwise.
+ */
+uint32_t
+qpu_encode_small_immediate(uint32_t i)
+{
+        if (i <= 15)
+                return i;
+        if ((int)i < 0 && (int)i >= -16)
+                return i + 32;
+
+        switch (i) {
+        case 0x3f800000:
+                return 32;
+        case 0x40000000:
+                return 33;
+        case 0x40800000:
+                return 34;
+        case 0x41000000:
+                return 35;
+        case 0x41800000:
+                return 36;
+        case 0x42000000:
+                return 37;
+        case 0x42800000:
+                return 38;
+        case 0x43000000:
+                return 39;
+        case 0x3b800000:
+                return 40;
+        case 0x3c000000:
+                return 41;
+        case 0x3c800000:
+                return 42;
+        case 0x3d000000:
+                return 43;
+        case 0x3d800000:
+                return 44;
+        case 0x3e000000:
+                return 45;
+        case 0x3e800000:
+                return 46;
+        case 0x3f000000:
+                return 47;
+        }
+
+        return ~0;
+}
+
 void
 qpu_serialize_one_inst(struct vc4_compile *c, uint64_t inst)
 {
         if (c->qpu_inst_count >= c->qpu_inst_size) {
                 c->qpu_inst_size = MAX2(16, c->qpu_inst_size * 2);
-                c->qpu_insts = realloc(c->qpu_insts,
-                                       c->qpu_inst_size * sizeof(uint64_t));
+                c->qpu_insts = reralloc(c, c->qpu_insts,
+                                        uint64_t, c->qpu_inst_size);
         }
         c->qpu_insts[c->qpu_inst_count++] = inst;
 }