From: Jacob Lifshay <programmerjake@gmail.com>
Date: Sat, 13 May 2023 01:06:47 +0000 (-0700)
Subject: add rest of bfp_* helpers needed to run fcvt js test
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=74f645dd6b709dd131856a561bb85ef15a9414c8;p=openpower-isa.git

add rest of bfp_* helpers needed to run fcvt js test
---

diff --git a/openpower/isafunctions/bfp.mdwn b/openpower/isafunctions/bfp.mdwn
index 4cf13db8..7ab2ab2b 100644
--- a/openpower/isafunctions/bfp.mdwn
+++ b/openpower/isafunctions/bfp.mdwn
@@ -132,6 +132,36 @@ section 7.6.2.2
                 result.exponent <- result.exponent - 1
         return result
 
+    def bfp_CONVERT_FROM_SI128(x):
+        # x is a 128-bit signed integer value.
+
+        result <- BFPState()
+        result.sign <- 0
+        result.exponent <- 0
+        result.significand <- 0
+        result.class.SNaN <- 0
+        result.class.QNaN <- 0
+        result.class.Infinity <- 0
+        result.class.Zero <- 0
+        result.class.Denormal <- 0
+        result.class.Normal <- 0
+
+        if x = 0x0000_0000_0000_0000_0000_0000_0000_0000 then
+            result.class.Zero <- 1
+        else
+            result.class.Normal <- 1
+            result.sign <- x[0]
+            result.exponent <- 128
+            result.significand[0:128] <- EXTS(x)
+
+            if result.significand[0] = 1 then
+                result.sign <- 1
+                result.significand[0:128] <- -result.significand[0:128]
+            do while result.significand[0] = 0
+                result.significand <- result.significand * 2
+                result.exponent <- result.exponent - 1
+        return result
+
     def bfp_CONVERT_FROM_UI128(x):
         # x is a 128-bit unsigned integer value.
 
@@ -311,4 +341,38 @@ section 7.6.2.2
         # binary floating-point working format.
         result <- x
         result.sign <- 0
-        return result
\ No newline at end of file
+        return result
+
+    def si128_CONVERT_FROM_BFP(x):
+        # x is an integer value represented in the
+        # binary floating-point working format.
+
+        if IsNaN(x) then
+            vxcvi_flag <- 1
+            if IsSNaN(x) then vxsnan_flag <- 1
+            return 0x8000_0000_0000_0000_0000_0000_0000_0000
+        else
+            temp_xx <- xx_flag
+            temp_inc <- inc_flag
+            rnd <- bfp_ROUND_TO_INTEGER_TRUNC(x)
+            # TODO: does the spec say these are preserved?
+            xx_flag <- temp_xx
+            inc_flag <- temp_inc
+            exponent <- rnd.exponent
+            significand <- rnd.significand
+            si128max <- bfp_CONVERT_FROM_SI128(0b0 || [1] * 127)
+            si128min <- bfp_CONVERT_FROM_SI128(0b1 || [0] * 127)
+            if bfp_COMPARE_GT(rnd, si128max) then
+                vxcvi_flag <- 1
+                return 0x7FFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF
+            if bfp_COMPARE_LT(rnd, si128min) then
+                vxcvi_flag <- 1
+                return 0x8000_0000_0000_0000_0000_0000_0000_0000
+            else
+                if ¬bfp_COMPARE_EQ(rnd, x) then xx_flag <- 1
+                else xx_flag <- 0  # TODO: does the spec specify this?
+                inc_flag <- 0
+                # TODO: spec says this is logical shift right:
+                significand <- significand[0:127] / pow(2, 127 - exponent)
+                if IsNeg(rnd) then significand <- -significand
+                return significand[0:127]
diff --git a/src/openpower/decoder/helpers.py b/src/openpower/decoder/helpers.py
index 982f1396..2c937134 100644
--- a/src/openpower/decoder/helpers.py
+++ b/src/openpower/decoder/helpers.py
@@ -883,6 +883,13 @@ def IsZero(v):
     raise NotImplementedError("not yet implemented for non-BFPState values")
 
 
+def SetFX(fpscr, field):
+    assert isinstance(fpscr, FPSCRState), "SetFX only works on FPSCR fields"
+    if eq(getattr(fpscr, field), SelectableInt(0, 1)):
+        setattr(fpscr, field, SelectableInt(1, 1))
+        fpscr.FX = SelectableInt(1, 1)
+
+
 class ISACallerHelper:
     def __init__(self, XLEN, FPSCR):
         self.__XLEN = XLEN