From 33137f8a660750d7d8598c7e467f4ccc8dc5ef85 Mon Sep 17 00:00:00 2001
From: Michael Matz <address@hidden>
Date: Sat, 23 Mar 2013 04:53:44 +0100
Subject: [PATCH] Fix the pstate flags helpers

ADCS and SBCS/SUBS sometimes gave the wrong results
for the C and V flags.  This fixes it.
---
 target-arm/helper-a64.c | 52 ++++++++++++-------------------------------------
 1 file changed, 12 insertions(+), 40 deletions(-)

diff --git a/target-arm/helper-a64.c b/target-arm/helper-a64.c
index 4375bf0..4fcb09b 100644
--- a/target-arm/helper-a64.c
+++ b/target-arm/helper-a64.c
@@ -7,8 +7,6 @@
 
 uint32_t HELPER(pstate_add)(uint32_t pstate, uint64_t a1, uint64_t a2, uint64_t ar)
 {
-    int64_t s1 = a1;
-    int64_t s2 = a2;
     int64_t sr = ar;
 
     pstate &= ~(PSTATE_N | PSTATE_Z | PSTATE_C | PSTATE_V);
@@ -21,11 +19,15 @@ uint32_t HELPER(pstate_add)(uint32_t pstate, uint64_t a1, uint64_t a2, uint64_t
         pstate |= PSTATE_Z;
     }
 
-    if (ar && (ar < a1)) {
+    if (ar < a1) {
         pstate |= PSTATE_C;
+    } else if (ar != (a1 + a2) && ar == a1) {
+	/* If result isn't what we expect it must be because we added
+	   in some carry.  If so we also produce a carry when ar == a1. */
+	pstate |= PSTATE_C;
     }
 
-    if ((s1 > 0 && s2 > 0 && sr < 0) || (s1 < 0 && s2 < 0 && sr > 0)) {
+    if ((int64_t)((a1 ^ a2 ^ -1) & (a1 ^ ar)) < 0) {
         pstate |= PSTATE_V;
     }
 
@@ -38,8 +40,6 @@ uint32_t HELPER(pstate_add32)(uint32_t pstate, uint64_t x1, uint64_t x2, uint64_
     uint32_t a2 = x2;
     uint32_t ar = xr;
 
-    int32_t s1 = a1;
-    int32_t s2 = a2;
     int32_t sr = ar;
 
     pstate &= ~(PSTATE_N | PSTATE_Z | PSTATE_C | PSTATE_V);
@@ -52,11 +52,13 @@ uint32_t HELPER(pstate_add32)(uint32_t pstate, uint64_t x1, uint64_t x2, uint64_
         pstate |= PSTATE_Z;
     }
 
-    if (ar && (ar < a1)) {
+    if (ar < a1) {
         pstate |= PSTATE_C;
+    } else if (ar != (a1 + a2) && ar == a1) {
+	pstate |= PSTATE_C;
     }
 
-    if ((s1 > 0 && s2 > 0 && sr < 0) || (s1 < 0 && s2 < 0 && sr > 0)) {
+    if ((int32_t)((a1 ^ a2 ^ -1) & (a1 ^ ar)) < 0) {
         pstate |= PSTATE_V;
     }
 
@@ -65,23 +67,7 @@ uint32_t HELPER(pstate_add32)(uint32_t pstate, uint64_t x1, uint64_t x2, uint64_
 
 uint32_t HELPER(pstate_sub)(uint32_t pstate, uint64_t a1, uint64_t a2, uint64_t ar)
 {
-    int64_t sr = ar;
-    int64_t s1 = a1;
-    int64_t s2 = a2;
-
-    pstate = helper_pstate_add(pstate, a1, a2, ar);
-
-    pstate &= ~(PSTATE_C | PSTATE_V);
-
-    if (a2 <= a1) {
-        pstate |= PSTATE_C;
-    }
-
-    /* XXX check if this is the only special case */
-    if ((!a1 && a2 == 0x8000000000000000ULL) || (s1 > 0 && s2 < 0 && sr < 0) || (s1 < 0 && s2 > 0 && sr > 0)) {
-        pstate |= PSTATE_V;
-    }
-
+    pstate = helper_pstate_add(pstate, a1, ~a2, ar);
     return pstate;
 }
 
@@ -90,22 +76,8 @@ uint32_t HELPER(pstate_sub32)(uint32_t pstate, uint64_t x1, uint64_t x2, uint64_
     uint32_t a1 = x1;
     uint32_t a2 = x2;
     uint32_t ar = xr;
-    int32_t sr = ar;
-    int32_t s1 = a1;
-    int32_t s2 = a2;
-
-    pstate = helper_pstate_add32(pstate, a1, a2, ar);
-
-    pstate &= ~(PSTATE_C | PSTATE_V);
-
-    if (a2 <= a1) {
-        pstate |= PSTATE_C;
-    }
-
-    if ((!a1 && a2 == 0x80000000ULL) || (s1 > 0 && s2 < 0 && sr < 0) || (s1 < 0 && s2 > 0 && sr > 0)) {
-        pstate |= PSTATE_V;
-    }
 
+    pstate = helper_pstate_add32(pstate, a1, ~a2, ar);
     return pstate;
 }
 
-- 
1.8.1.4