[ELF] - Linkerscript: support MIN and MAX.

[grimar]

Summary

Sample 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.

[• espindola]

The implementation looks fine, but is anything using it?

[• espindola]

I see that this is for convenience in PR36768.

LGTM since it is trivial.

[ruiu]

LGTM

I'm fine with this too.

ELF/ScriptParser.cpp

Expr ScriptParser::readPrimary() {
   if (Tok == "LOADADDR") {
     StringRef Name = readParenLiteral();
     OutputSection *Cmd = Script->getOrCreateOutputSection(Name);
     return [=] {
       checkIfExists(Cmd, Location);
       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) {
       setError("memory region not defined: " + Name);
       return [] { return 0; };
     }
     return [=] { return Script->MemoryRegions[Name]->Origin; };
   }

test/ELF/linkerscript/operators.test

SECTIONS {
   maxpagesize = CONSTANT (MAXPAGESIZE);
   commonpagesize = CONSTANT (COMMONPAGESIZE);
   . = 0xfff0;
   datasegmentalign = DATA_SEGMENT_ALIGN (0xffff, 0);
   datasegmentalign2 = DATA_SEGMENT_ALIGN (0, 0);
   _end = .;
   minus_rel = _end - 0x10;
   minus_abs = _end - _start;
+  max = MAX(11, 22);
+  min = MIN(11, 22);
 }
 
 # CHECK: 00000000000006 *ABS* 00000000 plus
 # CHECK: 00000000000004 *ABS* 00000000 minus
 # CHECK: 00000000000003 *ABS* 00000000 div
 # CHECK: 00000000000006 *ABS* 00000000 mod
 # CHECK: 00000000000007 *ABS* 00000000 mul
 # CHECK: 00000000000005 *ABS* 00000000 nospace

 # CHECK: 00000000000009 *ABS* 00000000 precedence1
 # CHECK: 00000000000009 *ABS* 00000000 precedence2
 # CHECK: 00000000001000 *ABS* 00000000 maxpagesize
 # CHECK: 00000000001000 *ABS* 00000000 commonpagesize
 # CHECK: 0000000000ffff *ABS* 00000000 datasegmentalign
 # CHECK: 0000000000fff0 *ABS* 00000000 datasegmentalign2
 # CHECK: 0000000000ffe0 .text 00000000 minus_rel
 # CHECK: 0000000000fff0 *ABS* 00000000 minus_abs
+# CHECK: 00000000000016 *ABS* 00000000 max
+# CHECK: 0000000000000b *ABS* 00000000 min
 
 ## Mailformed number error.
 # RUN: echo "SECTIONS { . = 0x12Q41; }" > %t.script
 # RUN: not ld.lld %t --script %t.script -o %t2 2>&1 | \
 # RUN:  FileCheck --check-prefix=NUMERR %s
 # NUMERR: malformed number: 0x12Q41
 
 ## Missing closing bracket.