From a01c09c3934d3f859bf4bea6b4e583f25291b643 Mon Sep 17 00:00:00 2001
From: jsmall-nvidia <jsmall@nvidia.com>
Date: Thu, 9 Apr 2020 15:43:09 -0400
Subject: Literal folding on other operators (#1314)

* Fold prefix operators if they prefix an int literal.

* Make test case a bit more convoluted.

* Remove ++ and -- as not appropriate for folding of literals.

* Set output buffer name.
---
 source/slang/slang-parser.cpp | 61 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 48 insertions(+), 13 deletions(-)

(limited to 'source/slang')

diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index 4ce4c49b5..170178932 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -4706,29 +4706,63 @@ namespace Slang
         }
     }
 
+    static IRIntegerValue _foldIntegerPrefixOp(TokenType tokenType, IRIntegerValue value)
+    {
+        switch (tokenType)
+        {
+            case TokenType::OpNot:      return !value;
+            case TokenType::OpBitNot:   return ~value;
+            case TokenType::OpAdd:      return value;
+            case TokenType::OpSub:      return -value;
+            default:
+            {
+                SLANG_ASSERT(!"Unexpected op");
+                return value;
+            }
+        }
+    }
+
+    static IRFloatingPointValue _foldFloatPrefixOp(TokenType tokenType, IRFloatingPointValue value)
+    {
+        switch (tokenType)
+        {
+            case TokenType::OpNot:      return !value;
+            case TokenType::OpAdd:      return value;
+            case TokenType::OpSub:      return -value;
+            default:
+            {
+                SLANG_ASSERT(!"Unexpected op");
+                return value;
+            }
+        }
+    }
+
     static RefPtr<Expr> parsePrefixExpr(Parser* parser)
     {
-        switch( peekTokenType(parser) )
+        auto tokenType = peekTokenType(parser);
+        switch( tokenType )
         {
         default:
             return parsePostfixExpr(parser);
 
+
         case TokenType::OpInc:
         case TokenType::OpDec:
+        {
+            RefPtr<PrefixExpr> prefixExpr = new PrefixExpr();
+            parser->FillPosition(prefixExpr.Ptr());
+            prefixExpr->FunctionExpr = parseOperator(parser);
+
+            auto arg = parsePrefixExpr(parser);
+
+            prefixExpr->Arguments.add(arg);
+            return prefixExpr;
+        }
         case TokenType::OpNot:
         case TokenType::OpBitNot:
         case TokenType::OpAdd:
-            {
-                RefPtr<PrefixExpr> prefixExpr = new PrefixExpr();
-                parser->FillPosition(prefixExpr.Ptr());
-                prefixExpr->FunctionExpr = parseOperator(parser);
-                prefixExpr->Arguments.add(parsePrefixExpr(parser));
-                return prefixExpr;
-            }
         case TokenType::OpSub:
             {
-                // Special case prefix sub (aka neg), so if it's on a literal, it produces a new literal
-
                 RefPtr<PrefixExpr> prefixExpr = new PrefixExpr();
                 parser->FillPosition(prefixExpr.Ptr());
                 prefixExpr->FunctionExpr = parseOperator(parser);
@@ -4739,7 +4773,7 @@ namespace Slang
                 {
                     RefPtr<IntegerLiteralExpr> newLiteral = new IntegerLiteralExpr(*intLit);
 
-                    IRIntegerValue value = -newLiteral->value;
+                    IRIntegerValue value = _foldIntegerPrefixOp(tokenType, newLiteral->value);
 
                     // Need to get the basic type, so we can fit to underlying type
                     if (auto basicExprType = as<BasicExpressionType>(intLit->type.type))
@@ -4753,13 +4787,14 @@ namespace Slang
                 else if (auto floatLit = as<FloatingPointLiteralExpr>(arg))
                 {
                     RefPtr<FloatingPointLiteralExpr> newLiteral = new FloatingPointLiteralExpr(*floatLit);
-                    newLiteral->value = -newLiteral->value;
+                    newLiteral->value = _foldFloatPrefixOp(tokenType, floatLit->value);
                     return newLiteral;
                 }
-                
+
                 prefixExpr->Arguments.add(arg);
                 return prefixExpr;
             }
+        
             break;
         }
     }
-- 
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