From: Jacob Lifshay <programmerjake@gmail.com>
Date: Wed, 26 Apr 2023 01:44:18 +0000 (-0700)
Subject: add fminmax pseudo-code
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=8967ddf3e3fbcc16b0dfe07dfd68453b2665e661;p=libreriscv.git

add fminmax pseudo-code
---

diff --git a/openpower/sv/rfc/ls013.mdwn b/openpower/sv/rfc/ls013.mdwn
index 08e5817eb..118003485 100644
--- a/openpower/sv/rfc/ls013.mdwn
+++ b/openpower/sv/rfc/ls013.mdwn
@@ -156,6 +156,64 @@ Note (3): TODO: icr if IEEE 754-2008 has min/maxMagNum like IEEE 754-2019's
     | PO  | FRT | FRA | FRB | FMM | XO | Rc |
 ```
 
+```
+    result <- [0] * 64
+    a <- (FRA)
+    b <- (FRB)
+    abs_a <- 0b0 || a[1:63]
+    abs_b <- 0b0 || b[1:63]
+    a_is_nan <- abs_a >u 0x7FF0_0000_0000_0000
+    a_is_snan <- a_is_nan and a[12] = 0
+    b_is_nan <- abs_b >u 0x7FF0_0000_0000_0000
+    b_is_snan <- b_is_nan and b[12] = 0
+    any_snan <- a_is_snan or b_is_snan
+    a_quieted <- a
+    a_quieted[12] = 1
+    b_quieted <- b
+    b_quieted[12] = 1
+    if a_is_nan or b_is_nan then
+        if FMM[2:3] = 0b00 then  # min/maxnum08
+            if a_is_snan then result <- a_quieted
+            else if b_is_snan then result <- b_quieted
+            else if a_is_nan and b_is_nan then result <- a_quieted
+            else if a_is_nan then result <- b
+            else result <- a
+        if FMM[2:3] = 0b01 then  # min/max19
+            if a_is_nan then result <- a_quieted
+            else result <- b_quieted
+        if FMM[2:3] = 0b10 then  # min/maxnum19
+            if a_is_nan and b_is_nan then result <- a_quieted
+            else if a_is_nan then result <- b
+            else result <- a
+        if FMM[2:3] = 0b11 then  # min/maxc
+            result <- b
+    else
+        cmp_l <- a
+        cmp_r <- b
+        if FMM[1] then  # min/maxmag
+            if abs_a != abs_b then
+                cmp_l <- abs_a
+                cmp_r <- abs_b
+        if FMM[2:3] = 0b11 then  # min/maxc
+            if abs_a = 0 then cmp_l <- 0
+            if abs_b = 0 then cmp_r <- 0
+        if FMM[0] then  # max
+            # swap cmp_* so comparison goes the other way
+            cmp_l, cmp_r <- cmp_r, cmp_l
+        if cmp_l[0] = 1 then
+            if cmp_r[0] = 0 then result <- a
+            else if cmp_l >u cmp_r then
+                # IEEE 754 is sign-magnitude,
+                # so bigger magnitude negative is smaller
+                result <- a
+            else result <- b
+        else if cmp_r[0] = 1 then result <- b
+        else if cmp_l <u cmp_r then result <- a
+        else result <- b
+    if any_snan then SetFX(FPSCR.VXSNAN)
+    if FPSCR.VE = 0 and ¬any_snan then (FRT) <- result
+```
+
 Compute the minimum/maximum of FRA and FRB, according to FMM, and store the
 result in FRT.