[PATCH 17/29] target/ppc: Move wait instruction to decodetree

[Chinmay Rath <rathc@linux.ibm.com>]

From: Ojaswin Mujoo <ojaswin@linux.ibm.com>

Implement wait instruction using decodetree with
proper handling of WC and PL fields across different ISA
versions. Since the opcode changed between ISA 2.x and 3.x
we have defined 2 different decodetree instructions that
are handled by the same helper.

The changes have been tested by comparing the tcg generated
before and after the change for wait instruction. The test
was repeated for 2 types of machines:

Power10 - which should use the newer wait implementation
e500mc - which should use older PPC_WAIT implementation

Both generated the same tcg ops with and without the change.
Further, with the changes we were able to boot into Fedora
distro as well.

Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Chinmay Rath <rathc@linux.ibm.com>
---
 target/ppc/insn32.decode                     |  15 +++
 target/ppc/translate.c                       |  91 -----------------
 target/ppc/translate/storage-ctrl-impl.c.inc | 100 +++++++++++++++++++
 3 files changed, 115 insertions(+), 91 deletions(-)

diff --git a/target/ppc/insn32.decode b/target/ppc/insn32.decode
index 67fb181542..3b8387b60c 100644
--- a/target/ppc/insn32.decode
+++ b/target/ppc/insn32.decode
@@ -1480,6 +1480,21 @@ ISYNC           010011 ----- ----- ----- 0010010110 -
 @XL_bfa         ...... bf:3 .. bfa:3 .. ..... ..... ..... .
 MCRF            010011 ... -- ... -- ----- 00000 00000 -       @XL_bfa
 
+# Wait Instructions
+
+# We can use the same X_wait argument set for both WAIT and older ISA2.x
+# compliant WAIT_2_x. Depending on the version, we may or may not use the
+# arguments. For more information, check do_wait() helper.
+
+&X_wait         wc pl
+@X_wait         ...... ..- wc:2 --- pl:2 ----- .......... -  &X_wait
+
+# According to ISA v3.1, bit 6 and 7 are implementation dependent and "unless
+# the intention is to use the implementation-dependent field, these bits must be
+# coded zero". Hence, we code them to 0.
+WAIT            011111 00-.. ---.. ----- 0000011110 -  @X_wait
+WAIT_ISA_2_X    011111 ---.. ---.. ----- 0000111110 -  @X_wait
+
 # Branch History Rolling Buffer (BHRB) Instructions
 
 &XFX_bhrbe      rt bhrbe
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index f7c7f53d82..2d5157080c 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -2727,95 +2727,6 @@ static inline void gen_check_tlb_flush(DisasContext *ctx, bool global)
 static inline void gen_check_tlb_flush(DisasContext *ctx, bool global) { }
 #endif
 
-/* wait */
-static void gen_wait(DisasContext *ctx)
-{
-    uint32_t wc;
-
-    if (ctx->insns_flags & PPC_WAIT) {
-        /* v2.03-v2.07 define an older incompatible 'wait' encoding. */
-
-        if (ctx->insns_flags2 & PPC2_PM_ISA206) {
-            /* v2.06 introduced the WC field. WC > 0 may be treated as no-op. */
-            wc = WC(ctx->opcode);
-        } else {
-            wc = 0;
-        }
-
-    } else if (ctx->insns_flags2 & PPC2_ISA300) {
-        /* v3.0 defines a new 'wait' encoding. */
-        wc = WC(ctx->opcode);
-        if (ctx->insns_flags2 & PPC2_ISA310) {
-            uint32_t pl = PL(ctx->opcode);
-
-            /* WC 1,2 may be treated as no-op. WC 3 is reserved. */
-            if (wc == 3) {
-                gen_invalid(ctx);
-                return;
-            }
-
-            /* PL 1-3 are reserved. If WC=2 then the insn is treated as noop. */
-            if (pl > 0 && wc != 2) {
-                gen_invalid(ctx);
-                return;
-            }
-
-        } else { /* ISA300 */
-            /* WC 1-3 are reserved */
-            if (wc > 0) {
-                gen_invalid(ctx);
-                return;
-            }
-        }
-
-    } else {
-        warn_report("wait instruction decoded with wrong ISA flags.");
-        gen_invalid(ctx);
-        return;
-    }
-
-    /*
-     * wait without WC field or with WC=0 waits for an exception / interrupt
-     * to occur.
-     */
-    if (wc == 0) {
-        TCGv_i32 t0 = tcg_constant_i32(1);
-        tcg_gen_st_i32(t0, tcg_env,
-                       -offsetof(PowerPCCPU, env) + offsetof(CPUState, halted));
-        /* Stop translation, as the CPU is supposed to sleep from now */
-        gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);
-    }
-
-    /*
-     * Other wait types must not just wait until an exception occurs because
-     * ignoring their other wake-up conditions could cause a hang.
-     *
-     * For v2.06 and 2.07, wc=1,2,3 are architected but may be implemented as
-     * no-ops.
-     *
-     * wc=1 and wc=3 explicitly allow the instruction to be treated as a no-op.
-     *
-     * wc=2 waits for an implementation-specific condition, such could be
-     * always true, so it can be implemented as a no-op.
-     *
-     * For v3.1, wc=1,2 are architected but may be implemented as no-ops.
-     *
-     * wc=1 (waitrsv) waits for an exception or a reservation to be lost.
-     * Reservation-loss may have implementation-specific conditions, so it
-     * can be implemented as a no-op.
-     *
-     * wc=2 waits for an exception or an amount of time to pass. This
-     * amount is implementation-specific so it can be implemented as a
-     * no-op.
-     *
-     * ISA v3.1 allows for execution to resume "in the rare case of
-     * an implementation-dependent event", so in any case software must
-     * not depend on the architected resumption condition to become
-     * true, so no-op implementations should be architecturally correct
-     * (if suboptimal).
-     */
-}
-
 #if defined(TARGET_PPC64)
 static void gen_doze(DisasContext *ctx)
 {
@@ -5197,8 +5108,6 @@ GEN_HANDLER(lswx, 0x1F, 0x15, 0x10, 0x00000001, PPC_STRING),
 GEN_HANDLER(stswi, 0x1F, 0x15, 0x16, 0x00000001, PPC_STRING),
 GEN_HANDLER(stswx, 0x1F, 0x15, 0x14, 0x00000001, PPC_STRING),
 /* ISA v3.0 changed the extended opcode from 62 to 30 */
-GEN_HANDLER(wait, 0x1F, 0x1E, 0x01, 0x039FF801, PPC_WAIT),
-GEN_HANDLER_E(wait, 0x1F, 0x1E, 0x00, 0x039CF801, PPC_NONE, PPC2_ISA300),
 GEN_HANDLER(rfi, 0x13, 0x12, 0x01, 0x03FF8001, PPC_FLOW),
 #if defined(TARGET_PPC64)
 GEN_HANDLER(rfid, 0x13, 0x12, 0x00, 0x03FF8001, PPC_64B),
diff --git a/target/ppc/translate/storage-ctrl-impl.c.inc b/target/ppc/translate/storage-ctrl-impl.c.inc
index 943229c438..21c7999d5d 100644
--- a/target/ppc/translate/storage-ctrl-impl.c.inc
+++ b/target/ppc/translate/storage-ctrl-impl.c.inc
@@ -270,3 +270,103 @@ static bool do_tlbie(DisasContext *ctx, arg_X_tlbie *a, bool local)
 
 TRANS_FLAGS(MEM_TLBIE, TLBIE, do_tlbie, false)
 TRANS_FLAGS(MEM_TLBIE, TLBIEL, do_tlbie, true)
+
+/*
+ * Decodetree populates a->wc and a->pl based on ISA v3.1, however they may
+ * or may not be used based on the ISA:
+ *   For ISA < 2.06 - both wc and pl are ignored
+ *   For ISA == 2.06, 2.07, 3.0 - wc is used and pl is ignored
+ *   For ISA 3.1 - both wc and pl are used
+ */
+static bool do_wait(DisasContext *ctx, arg_X_wait *a)
+{
+    uint32_t wc;
+
+    if (ctx->insns_flags & PPC_WAIT) {
+        /* v2.03-v2.07 define an older incompatible 'wait' encoding. */
+
+        if (ctx->insns_flags2 & PPC2_PM_ISA206) {
+            /* v2.06 introduced the WC field. WC > 0 may be treated as no-op. */
+            wc = a->wc;
+        } else {
+            wc = 0;
+        }
+
+    } else if (ctx->insns_flags2 & PPC2_ISA300) {
+        /* v3.0 defines a new 'wait' encoding. */
+        wc = a->wc;
+        if (ctx->insns_flags2 & PPC2_ISA310) {
+            uint32_t pl = a->pl;
+
+            /* WC 1,2 may be treated as no-op. WC 3 is reserved. */
+            if (wc == 3) {
+                gen_invalid(ctx);
+                return true;
+            }
+
+            /* PL 1-3 are reserved. If WC=2 then the insn is treated as noop. */
+            if (pl > 0 && wc != 2) {
+                gen_invalid(ctx);
+                return true;
+            }
+
+        } else { /* ISA300 */
+            /* WC 1-3 are reserved */
+            if (wc > 0) {
+                gen_invalid(ctx);
+                return true;
+            }
+        }
+
+    } else {
+        warn_report("wait instruction decoded with wrong ISA flags.");
+        gen_invalid(ctx);
+        return true;
+    }
+
+    /*
+     * wait without WC field or with WC=0 waits for an exception / interrupt
+     * to occur.
+     */
+    if (wc == 0) {
+        TCGv_i32 t0 = tcg_constant_i32(1);
+        tcg_gen_st_i32(t0, tcg_env,
+                       -offsetof(PowerPCCPU, env) + offsetof(CPUState, halted));
+        /* Stop translation, as the CPU is supposed to sleep from now */
+        gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);
+    }
+
+    /*
+     * Other wait types must not just wait until an exception occurs because
+     * ignoring their other wake-up conditions could cause a hang.
+     *
+     * For v2.06 and 2.07, wc=1,2,3 are architected but may be implemented as
+     * no-ops.
+     *
+     * wc=1 and wc=3 explicitly allow the instruction to be treated as a no-op.
+     *
+     * wc=2 waits for an implementation-specific condition, such could be
+     * always true, so it can be implemented as a no-op.
+     *
+     * For v3.1, wc=1,2 are architected but may be implemented as no-ops.
+     *
+     * wc=1 (waitrsv) waits for an exception or a reservation to be lost.
+     * Reservation-loss may have implementation-specific conditions, so it
+     * can be implemented as a no-op.
+     *
+     * wc=2 waits for an exception or an amount of time to pass. This
+     * amount is implementation-specific so it can be implemented as a
+     * no-op.
+     *
+     * ISA v3.1 allows for execution to resume "in the rare case of
+     * an implementation-dependent event", so in any case software must
+     * not depend on the architected resumption condition to become
+     * true, so no-op implementations should be architecturally correct
+     * (if suboptimal).
+     */
+     return true;
+}
+
+TRANS_FLAGS(WAIT, WAIT_ISA_2_X, do_wait)
+TRANS_FLAGS2(ISA300, WAIT, do_wait)
+
-- 
2.55.0