commit 595341b150312d2407bd43304449bf39ec3e1fa8
Author: Julian Seward <jseward@acm.org>
Date:   Sat Nov 13 19:59:07 2021 +0100

    amd64 front end: add more spec rules:
    
       S  after SHRQ
       Z  after SHLQ
       NZ after SHLQ
       Z  after SHLL
       S  after SHLL
    
    The lack of at least one of these was observed to cause occasional false
    positives in Memcheck.
    
    Plus add commented-out cases so as to complete the set of 12 rules
    {Z,NZ,S,NS} after {SHRQ,SHLQ,SHLL}.  The commented-out ones are commented
    out because I so far didn't find any use cases for them.

diff --git a/VEX/priv/guest_amd64_helpers.c b/VEX/priv/guest_amd64_helpers.c
index 9d61e7a0f..ba71c1b62 100644
--- a/VEX/priv/guest_amd64_helpers.c
+++ b/VEX/priv/guest_amd64_helpers.c
@@ -1823,16 +1823,26 @@ IRExpr* guest_amd64_spechelper ( const HChar* function_name,
       /*---------------- SHRQ ----------------*/
 
       if (isU64(cc_op, AMD64G_CC_OP_SHRQ) && isU64(cond, AMD64CondZ)) {
-         /* SHRQ, then Z --> test dep1 == 0 */
+         /* SHRQ, then Z --> test result[63:0] == 0 */
          return unop(Iop_1Uto64,
                      binop(Iop_CmpEQ64, cc_dep1, mkU64(0)));
       }
       if (isU64(cc_op, AMD64G_CC_OP_SHRQ) && isU64(cond, AMD64CondNZ)) {
-         /* SHRQ, then NZ --> test dep1 != 0 */
+         /* SHRQ, then NZ --> test result[63:0] != 0 */
          return unop(Iop_1Uto64,
                      binop(Iop_CmpNE64, cc_dep1, mkU64(0)));
       }
 
+      if (isU64(cc_op, AMD64G_CC_OP_SHRQ) && isU64(cond, AMD64CondS)) {
+         /* SHRQ, then S --> (ULong)result[63] (result is in dep1) */
+         return binop(Iop_Shr64, cc_dep1, mkU8(63));
+      }
+      // No known test case for this, hence disabled:
+      //if (isU64(cc_op, AMD64G_CC_OP_SHRQ) && isU64(cond, AMD64CondNS)) {
+      //   /* SHRQ, then NS --> (ULong) ~ result[63] */
+      //   vassert(0);
+      //}
+
       /*---------------- SHRL ----------------*/
 
       if (isU64(cc_op, AMD64G_CC_OP_SHRL) && isU64(cond, AMD64CondZ)) {
@@ -1881,6 +1891,52 @@ IRExpr* guest_amd64_spechelper ( const HChar* function_name,
       //                     mkU32(0)));
       //}
 
+      /*---------------- SHLQ ----------------*/
+
+      if (isU64(cc_op, AMD64G_CC_OP_SHLQ) && isU64(cond, AMD64CondZ)) {
+         /* SHLQ, then Z --> test dep1 == 0 */
+         return unop(Iop_1Uto64,
+                     binop(Iop_CmpEQ64, cc_dep1, mkU64(0)));
+      }
+      if (isU64(cc_op, AMD64G_CC_OP_SHLQ) && isU64(cond, AMD64CondNZ)) {
+         /* SHLQ, then NZ --> test dep1 != 0 */
+         return unop(Iop_1Uto64,
+                     binop(Iop_CmpNE64, cc_dep1, mkU64(0)));
+      }
+
+      //if (isU64(cc_op, AMD64G_CC_OP_SHLQ) && isU64(cond, AMD64CondS)) {
+      //   /* SHLQ, then S --> (ULong)result[63] */
+      //   vassert(0);
+      //}
+      //if (isU64(cc_op, AMD64G_CC_OP_SHLQ) && isU64(cond, AMD64CondNS)) {
+      //   /* SHLQ, then NS --> (ULong) ~ result[63] */
+      //   vassert(0);
+      //}
+
+      /*---------------- SHLL ----------------*/
+
+      if (isU64(cc_op, AMD64G_CC_OP_SHLL) && isU64(cond, AMD64CondZ)) {
+         /* SHLL, then Z --> test result[31:0] == 0 */
+         return unop(Iop_1Uto64,
+                     binop(Iop_CmpEQ32, unop(Iop_64to32, cc_dep1),
+                           mkU32(0)));
+      }
+      //if (isU64(cc_op, AMD64G_CC_OP_SHLL) && isU64(cond, AMD64CondNZ)) {
+      //   /* SHLL, then NZ --> test dep1 != 0 */
+      //   vassert(0);
+      //}
+
+      if (isU64(cc_op, AMD64G_CC_OP_SHLL) && isU64(cond, AMD64CondS)) {
+         /* SHLL, then S --> (ULong)result[31] */
+         return binop(Iop_And64,
+                      binop(Iop_Shr64, cc_dep1, mkU8(31)),
+                      mkU64(1));
+      }
+      //if (isU64(cc_op, AMD64G_CC_OP_SHLL) && isU64(cond, AMD64CondNS)) {
+      //   /* SHLL, then NS --> (ULong) ~ result[31] */
+      //   vassert(0);
+      //}
+
       /*---------------- COPY ----------------*/
       /* This can happen, as a result of amd64 FP compares: "comisd ... ;
          jbe" for example. */