[ELF] - Linkerscript: support MIN and MAX.

Sample for the OVERLAY command from the spec 
(https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/4/html/Using_ld_the_GNU_Linker/sections.html)
uses MAX command that we do not support currently:

. = 0x1000 + MAX (SIZEOF (.text0), SIZEOF (.text1));

This patch implements support for MIN and MAX.

Differential revision: https://reviews.llvm.org/D44734

llvm-svn: 328696

1 files changed, 10 insertions, 0 deletions

diff --git a/lld/ELF/ScriptParser.cpp b/lld/ELF/ScriptParser.cpp
index 6f16c45baab..ff650d8ef87 100644
--- a/lld/ELF/ScriptParser.cpp
+++ b/lld/ELF/ScriptParser.cpp
@@ -1097,6 +1097,16 @@ Expr ScriptParser::readPrimary() {
       return Cmd->getLMA();
     };
   }
+  if (Tok == "MAX" || Tok == "MIN") {
+    expect("(");
+    Expr A = readExpr();
+    expect(",");
+    Expr B = readExpr();
+    expect(")");
+    if (Tok == "MIN")
+      return [=] { return std::min(A().getValue(), B().getValue()); };
+    return [=] { return std::max(A().getValue(), B().getValue()); };
+  }
   if (Tok == "ORIGIN") {
     StringRef Name = readParenLiteral();
     if (Script->MemoryRegions.count(Name) == 0) {