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Re: [PATCH 04/72] accel/tcg: Use add/sub overflow routines in tcg-runtim


From: David Hildenbrand
Subject: Re: [PATCH 04/72] accel/tcg: Use add/sub overflow routines in tcg-runtime-gvec.c
Date: Tue, 11 May 2021 11:46:16 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1

On 08.05.21 03:46, Richard Henderson wrote:
Obvious uses of the new functions.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
  accel/tcg/tcg-runtime-gvec.c | 36 ++++++++++++++++--------------------
  1 file changed, 16 insertions(+), 20 deletions(-)

diff --git a/accel/tcg/tcg-runtime-gvec.c b/accel/tcg/tcg-runtime-gvec.c
index 521da4a813..ac7d28c251 100644
--- a/accel/tcg/tcg-runtime-gvec.c
+++ b/accel/tcg/tcg-runtime-gvec.c
@@ -1073,9 +1073,8 @@ void HELPER(gvec_ssadd32)(void *d, void *a, void *b, 
uint32_t desc)
      for (i = 0; i < oprsz; i += sizeof(int32_t)) {
          int32_t ai = *(int32_t *)(a + i);
          int32_t bi = *(int32_t *)(b + i);
-        int32_t di = ai + bi;
-        if (((di ^ ai) &~ (ai ^ bi)) < 0) {
-            /* Signed overflow.  */
+        int32_t di;
+        if (sadd32_overflow(ai, bi, &di)) {
              di = (di < 0 ? INT32_MAX : INT32_MIN);
          }
          *(int32_t *)(d + i) = di;
@@ -1091,9 +1090,8 @@ void HELPER(gvec_ssadd64)(void *d, void *a, void *b, 
uint32_t desc)
      for (i = 0; i < oprsz; i += sizeof(int64_t)) {
          int64_t ai = *(int64_t *)(a + i);
          int64_t bi = *(int64_t *)(b + i);
-        int64_t di = ai + bi;
-        if (((di ^ ai) &~ (ai ^ bi)) < 0) {
-            /* Signed overflow.  */
+        int64_t di;
+        if (sadd64_overflow(ai, bi, &di)) {
              di = (di < 0 ? INT64_MAX : INT64_MIN);
          }
          *(int64_t *)(d + i) = di;
@@ -1143,9 +1141,8 @@ void HELPER(gvec_sssub32)(void *d, void *a, void *b, 
uint32_t desc)
      for (i = 0; i < oprsz; i += sizeof(int32_t)) {
          int32_t ai = *(int32_t *)(a + i);
          int32_t bi = *(int32_t *)(b + i);
-        int32_t di = ai - bi;
-        if (((di ^ ai) & (ai ^ bi)) < 0) {
-            /* Signed overflow.  */
+        int32_t di;
+        if (ssub32_overflow(ai, bi, &di)) {
              di = (di < 0 ? INT32_MAX : INT32_MIN);
          }
          *(int32_t *)(d + i) = di;
@@ -1161,9 +1158,8 @@ void HELPER(gvec_sssub64)(void *d, void *a, void *b, 
uint32_t desc)
      for (i = 0; i < oprsz; i += sizeof(int64_t)) {
          int64_t ai = *(int64_t *)(a + i);
          int64_t bi = *(int64_t *)(b + i);
-        int64_t di = ai - bi;
-        if (((di ^ ai) & (ai ^ bi)) < 0) {
-            /* Signed overflow.  */
+        int64_t di;
+        if (ssub64_overflow(ai, bi, &di)) {
              di = (di < 0 ? INT64_MAX : INT64_MIN);
          }
          *(int64_t *)(d + i) = di;
@@ -1209,8 +1205,8 @@ void HELPER(gvec_usadd32)(void *d, void *a, void *b, 
uint32_t desc)
      for (i = 0; i < oprsz; i += sizeof(uint32_t)) {
          uint32_t ai = *(uint32_t *)(a + i);
          uint32_t bi = *(uint32_t *)(b + i);
-        uint32_t di = ai + bi;
-        if (di < ai) {
+        uint32_t di;
+        if (uadd32_overflow(ai, bi, &di)) {
              di = UINT32_MAX;
          }
          *(uint32_t *)(d + i) = di;
@@ -1226,8 +1222,8 @@ void HELPER(gvec_usadd64)(void *d, void *a, void *b, 
uint32_t desc)
      for (i = 0; i < oprsz; i += sizeof(uint64_t)) {
          uint64_t ai = *(uint64_t *)(a + i);
          uint64_t bi = *(uint64_t *)(b + i);
-        uint64_t di = ai + bi;
-        if (di < ai) {
+        uint64_t di;
+        if (uadd64_overflow(ai, bi, &di)) {
              di = UINT64_MAX;
          }
          *(uint64_t *)(d + i) = di;
@@ -1273,8 +1269,8 @@ void HELPER(gvec_ussub32)(void *d, void *a, void *b, 
uint32_t desc)
      for (i = 0; i < oprsz; i += sizeof(uint32_t)) {
          uint32_t ai = *(uint32_t *)(a + i);
          uint32_t bi = *(uint32_t *)(b + i);
-        uint32_t di = ai - bi;
-        if (ai < bi) {
+        uint32_t di;
+        if (usub32_overflow(ai, bi, &di)) {
              di = 0;
          }
          *(uint32_t *)(d + i) = di;
@@ -1290,8 +1286,8 @@ void HELPER(gvec_ussub64)(void *d, void *a, void *b, 
uint32_t desc)
      for (i = 0; i < oprsz; i += sizeof(uint64_t)) {
          uint64_t ai = *(uint64_t *)(a + i);
          uint64_t bi = *(uint64_t *)(b + i);
-        uint64_t di = ai - bi;
-        if (ai < bi) {
+        uint64_t di;
+        if (usub64_overflow(ai, bi, &di)) {
              di = 0;
          }
          *(uint64_t *)(d + i) = di;


Reviewed-by: David Hildenbrand <david@redhat.com>

--
Thanks,

David / dhildenb




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