Hexagon (target/hexagon) Improve code gen for predicated HVX instructions

The following improvements are made for predicated HVX instructions
    During gen_commit_hvx, unconditionally move the "new" value into
        the dest
    Don't set slot_cancelled
    Remove runtime bookkeeping of which registers were updated
    Reduce the cases where gen_log_vreg_write[_pair] is called
        It's only needed for special operands VxxV and VyV
    Remove gen_log_qreg_write

Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Anton Johansson <anjo@rev.ng>
Message-Id: <20230307025828.1612809-15-tsimpson@quicinc.com>

1 files changed, 5 insertions, 16 deletions

diff --git a/target/hexagon/README b/target/hexagon/README
index 365606f..ebafc78 100644
--- a/target/hexagon/README
+++ b/target/hexagon/README
@@ -136,12 +136,9 @@ For HVX vectors, the generator behaves slightly differently.  The wide vectors
 won't fit in a TCGv or TCGv_i64, so we pass TCGv_ptr variables to pass the
 address to helper functions.  Here's an example for an HVX vector-add-word
 istruction.
-    static void generate_V6_vaddw(
-                    CPUHexagonState *env,
-                    DisasContext *ctx,
-                    Insn *insn,
-                    Packet *pkt)
+    static void generate_V6_vaddw(DisasContext *ctx)
     {
+        Insn *insn __attribute__((unused)) = ctx->insn;
         const int VdN = insn->regno[0];
         const intptr_t VdV_off =
             ctx_future_vreg_off(ctx, VdN, 1, true);
@@ -157,9 +154,7 @@ istruction.
         TCGv_ptr VvV = tcg_temp_new_ptr();
         tcg_gen_addi_ptr(VuV, cpu_env, VuV_off);
         tcg_gen_addi_ptr(VvV, cpu_env, VvV_off);
-        TCGv slot = tcg_constant_tl(insn->slot);
-        gen_helper_V6_vaddw(cpu_env, VdV, VuV, VvV, slot);
-        gen_log_vreg_write(ctx, VdV_off, VdN, EXT_DFL, insn->slot, false);
+        gen_helper_V6_vaddw(cpu_env, VdV, VuV, VvV);
     }
 
 Notice that we also generate a variable named <operand>_off for each operand of
@@ -172,12 +167,9 @@ functions from tcg-op-gvec.h.  Here's the override for this instruction.
 Finally, we notice that the override doesn't use the TCGv_ptr variables, so
 we don't generate them when an override is present.  Here is what we generate
 when the override is present.
-    static void generate_V6_vaddw(
-                    CPUHexagonState *env,
-                    DisasContext *ctx,
-                    Insn *insn,
-                    Packet *pkt)
+    static void generate_V6_vaddw(DisasContext *ctx)
     {
+        Insn *insn __attribute__((unused)) = ctx->insn;
         const int VdN = insn->regno[0];
         const intptr_t VdV_off =
             ctx_future_vreg_off(ctx, VdN, 1, true);
@@ -188,7 +180,6 @@ when the override is present.
         const intptr_t VvV_off =
             vreg_src_off(ctx, VvN);
         fGEN_TCG_V6_vaddw({ fHIDE(int i;) fVFOREACH(32, i) { VdV.w[i] = VuV.w[i] + VvV.w[i] ; } });
-        gen_log_vreg_write(ctx, VdV_off, VdN, EXT_DFL, insn->slot, false);
     }
 
 We also generate an analyze_<tag> function for each instruction.  Currently,
@@ -281,10 +272,8 @@ For Hexagon Vector eXtensions (HVX), the following fields are used
     VRegs                       Vector registers
     future_VRegs                Registers to be stored during packet commit
     tmp_VRegs                   Temporary registers *not* stored during commit
-    VRegs_updated               Mask of predicated vector writes
     QRegs                       Q (vector predicate) registers
     future_QRegs                Registers to be stored during packet commit
-    QRegs_updated               Mask of predicated vector writes
 
 *** Debugging ***