Hexagon (target/hexagon) assignment to c4 should wait until packet commit

On Hexagon, c4 is an alias for predicate registers P3:0.  If we assign to
c4 inside a packet with reads from predicate registers, the predicate
reads should get the old values.

Test case added to tests/tcg/hexagon/preg_alias.c

Co-authored-by: Michael Lambert <mlambert@cuicinc.com>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <20220210021556.9217-13-tsimpson@quicinc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 47 insertions, 5 deletions

diff --git a/target/hexagon/genptr.c b/target/hexagon/genptr.c
index 4419d30..cd6af4b 100644
--- a/target/hexagon/genptr.c
+++ b/target/hexagon/genptr.c
@@ -1,5 +1,5 @@
 /*
- *  Copyright(c) 2019-2021 Qualcomm Innovation Center, Inc. All Rights Reserved.
+ *  Copyright(c) 2019-2022 Qualcomm Innovation Center, Inc. All Rights Reserved.
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -210,11 +210,15 @@ static inline void gen_read_ctrl_reg_pair(DisasContext *ctx, const int reg_num,
     }
 }
 
-static inline void gen_write_p3_0(TCGv control_reg)
+static void gen_write_p3_0(DisasContext *ctx, TCGv control_reg)
 {
+    TCGv hex_p8 = tcg_temp_new();
     for (int i = 0; i < NUM_PREGS; i++) {
-        tcg_gen_extract_tl(hex_pred[i], control_reg, i * 8, 8);
+        tcg_gen_extract_tl(hex_p8, control_reg, i * 8, 8);
+        gen_log_pred_write(ctx, i, hex_p8);
+        ctx_log_pred_write(ctx, i);
     }
+    tcg_temp_free(hex_p8);
 }
 
 /*
@@ -228,7 +232,7 @@ static inline void gen_write_ctrl_reg(DisasContext *ctx, int reg_num,
                                       TCGv val)
 {
     if (reg_num == HEX_REG_P3_0) {
-        gen_write_p3_0(val);
+        gen_write_p3_0(ctx, val);
     } else {
         gen_log_reg_write(reg_num, val);
         ctx_log_reg_write(ctx, reg_num);
@@ -250,7 +254,7 @@ static inline void gen_write_ctrl_reg_pair(DisasContext *ctx, int reg_num,
     if (reg_num == HEX_REG_P3_0) {
         TCGv val32 = tcg_temp_new();
         tcg_gen_extrl_i64_i32(val32, val);
-        gen_write_p3_0(val32);
+        gen_write_p3_0(ctx, val32);
         tcg_gen_extrh_i64_i32(val32, val);
         gen_log_reg_write(reg_num + 1, val32);
         tcg_temp_free(val32);
diff --git a/tests/tcg/hexagon/preg_alias.c b/tests/tcg/hexagon/preg_alias.c
index 79febec..b44a811 100644
--- a/tests/tcg/hexagon/preg_alias.c
+++ b/tests/tcg/hexagon/preg_alias.c
@@ -97,6 +97,42 @@ static inline void creg_alias_pair(unsigned int cval, PRegs *pregs)
   check(c5, 0xdeadbeef);
 }
 
+static void test_packet(void)
+{
+    /*
+     * Test that setting c4 inside a packet doesn't impact the predicates
+     * that are read during the packet.
+     */
+
+    int result;
+    int old_val = 0x0000001c;
+
+    /* Test a predicated register transfer */
+    result = old_val;
+    asm (
+         "c4 = %1\n\t"
+         "{\n\t"
+         "    c4 = %2\n\t"
+         "    if (!p2) %0 = %3\n\t"
+         "}\n\t"
+         : "+r"(result)
+         : "r"(0xffffffff), "r"(0xff00ffff), "r"(0x837ed653)
+         : "p0", "p1", "p2", "p3");
+    check(result, old_val);
+
+    /* Test a predicated store */
+    result = 0xffffffff;
+    asm ("c4 = %0\n\t"
+         "{\n\t"
+         "    c4 = %1\n\t"
+         "    if (!p2) memw(%2) = #0\n\t"
+         "}\n\t"
+         :
+         : "r"(0), "r"(0xffffffff), "r"(&result)
+         : "p0", "p1", "p2", "p3", "memory");
+    check(result, 0x0);
+}
+
 int main()
 {
     int c4;
@@ -162,6 +198,8 @@ int main()
     creg_alias_pair(0xffffffff, &pregs);
     check(pregs.creg, 0xffffffff);
 
+    test_packet();
+
     puts(err ? "FAIL" : "PASS");
     return err;
 }