From: lkcl <lkcl@web>
Date: Wed, 11 Sep 2019 19:16:13 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: convert-csv-opcode-to-binary~4099
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=87cb4a75b55ac3eebc47afffba7fe67df7e62198;p=libreriscv.git

---

diff --git a/zfpacc_proposal.mdwn b/zfpacc_proposal.mdwn
index f7e4fa559..c2b642ed0 100644
--- a/zfpacc_proposal.mdwn
+++ b/zfpacc_proposal.mdwn
@@ -86,33 +86,15 @@ The values for the field facc to include the following:
 
 | facc  | mode    | description         |
 | ----- | ------- | ------------------- |
-| 0b00H | IEEE754 | correctly rounded   | 
-| 0b01H | ULP<1   | Unit Last Place < 1 | 
-| 0b10H | Vulkan  | Vulkan compliant    | 
-| 0b11H | Appx    | Machine Learning    |
-
-When bit 0 (H) of facc is set to zero, half-precision mode is
-disabled. When set, an automatic down conversion (FCVT) to half the
-instruction bitwidth (FP32 opcode would convert to FP16) on operands
-is performed, followed by the operation occuring at half precision,
-followed by automatic up conversion back to the instruction's bitwidth.
+| 0b000 | IEEE754 | correctly rounded   | 
+| 0b010 | ULP<1   | Unit Last Place < 1 | 
+| 0b100 | Vulkan  | Vulkan compliant    | 
+| 0b110 | Appx    | Machine Learning    
 
 Note that the format of the operands and result remain the same for
 all opcodes. The only change is in the *accuracy* of the result, not
 its format.
 
-Pseudocode for half accuracy mode:
-
-    def fpadd32(op1, op2):
-        if FCSR.facc.halfmode:
-            op1 = fcvt32to16(op1)
-            op2 = fcvt32to16(op2)
-            result = fpadd32(op1, op2)
-            return fcvt16to32(result)
-         else:
-            # TODO, reduced accuracy if requested
-            return op1 + op2
-
 ## Discussion
 
 maybe a solution would be to add an extra field to the fp control csr