From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Thu, 27 Oct 2022 14:47:53 +0000 (+0100)
Subject: fix dsrd pseudocode for new 3-in 2-out
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b38b5537c70792eded9cf8dd02adce48355905d6;p=openpower-isa.git

fix dsrd pseudocode for new 3-in 2-out
https://bugs.libre-soc.org/show_bug.cgi?id=937#c16
---

diff --git a/openpower/isa/svfixedarith.mdwn b/openpower/isa/svfixedarith.mdwn
index c1f79c0b..63453354 100644
--- a/openpower/isa/svfixedarith.mdwn
+++ b/openpower/isa/svfixedarith.mdwn
@@ -74,13 +74,11 @@ VA2-Form
 
 Pseudo-code:
 
-    hi <- (RC)
-    lo <- (RA)
-    sh <- (RB)
-    n <- sh[58:63]
-    mask[0:63] <- MASK(0, 63 - n)
-    v[0:63] <- (hi & ¬mask) | (lo & mask)
-    RT <- ROTL64(v, 64 - n)
+    n <- (RB)[58:63]
+    v <- ROTL128((RA) || [0]*64, 64-n)
+    mask <- ¬MASK(n, 63)
+    RT <- v[0:63] | ((RC) & mask)
+    RS <- v[64:127]
 
 Special Registers Altered:
 
diff --git a/src/openpower/test/bigint/bigint_cases.py b/src/openpower/test/bigint/bigint_cases.py
index 21223be3..76d15496 100644
--- a/src/openpower/test/bigint/bigint_cases.py
+++ b/src/openpower/test/bigint/bigint_cases.py
@@ -51,45 +51,21 @@ class BigIntCases(TestAccumulatorBase):
                 self.add_case(prog, gprs, expected=e)
 
     def case_dsrd0(self):
-        prog = Program(list(SVP64Asm(["dsrd 3,4,5,3"])), False)
+        prog = Program(list(SVP64Asm(["dsrd 3,4,5,6"])), False)
         for sh in _SHIFT_TEST_RANGE:
             with self.subTest(sh=sh):
                 gprs = [0] * 32
-                gprs[3] = 0x123456789ABCDEF
-                gprs[4] = 0xFEDCBA9876543210
-                gprs[5] = sh % 2 ** 64
-                e = ExpectedState(pc=4, int_regs=gprs)
-                v = (gprs[3] << 64) | gprs[4]
-                v >>= sh % 64
-                e.intregs[3] = v % 2 ** 64
-                self.add_case(prog, gprs, expected=e)
-
-    def case_dsrd1(self):
-        prog = Program(list(SVP64Asm(["dsrd 3,3,5,4"])), False)
-        for sh in _SHIFT_TEST_RANGE:
-            with self.subTest(sh=sh):
-                gprs = [0] * 32
-                gprs[3] = 0x123456789ABCDEF
+                gprs[6] = 0x123456789ABCDEF
                 gprs[4] = 0xFEDCBA9876543210
                 gprs[5] = sh % 2 ** 64
                 e = ExpectedState(pc=4, int_regs=gprs)
-                v = (gprs[4] << 64) | gprs[3]
+                v = (gprs[4] << 64)
                 v >>= sh % 64
-                e.intregs[3] = v % 2 ** 64
-                self.add_case(prog, gprs, expected=e)
-
-    def case_dsrd2(self):
-        prog = Program(list(SVP64Asm(["dsrd 3,5,3,4"])), False)
-        for sh in _SHIFT_TEST_RANGE:
-            with self.subTest(sh=sh):
-                gprs = [0] * 32
-                gprs[3] = sh % 2 ** 64
-                gprs[4] = 0xFEDCBA9876543210
-                gprs[5] = 0x02468ACE13579BDF
-                e = ExpectedState(pc=4, int_regs=gprs)
-                v = (gprs[4] << 64) | gprs[5]
-                v >>= sh % 64
-                e.intregs[3] = v % 2 ** 64
+                mask = ~((2 ** 64 - 1) >> (sh%64))
+                v |= (gprs[6] & mask)
+                print ("case_dsrd0", hex(mask), sh, hex(v))
+                e.intregs[3] = v         % 2 ** 64
+                e.intregs[6] = (v >> 64) % 2 ** 64
                 self.add_case(prog, gprs, expected=e)
 
 
@@ -224,7 +200,7 @@ class SVP64BigIntCases(TestAccumulatorBase):
         r4 (carry in at top-end)                            0x1234 << 192 =
         r18                   r17                   r16
         0x1234_0000_5678_0000 0x9ABC_0000_DEF0_0000 0x1357_0000_9BDF_0000 *
-        r4 (carry out i.e. scalar remainder)                       0xFEDC 
+        r4 (carry out i.e. scalar remainder)                       0xFEDC
         """
         prog = Program(list(SVP64Asm(["sv.divmod2du/mrr *16,*16,3,4"])), False)
         gprs = [0] * 32