[PATCH] D69411: [MC] Calculate difference of symbols in two fragments when possible

[Jian Cai via Phabricator via llvm-commits]

jcai19 updated this revision to Diff 226839.
jcai19 added a comment.

Update the test case.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D69411/new/

https://reviews.llvm.org/D69411

Files:
  llvm/lib/MC/MCExpr.cpp
  llvm/test/MC/AsmParser/directive_if_offset.s


Index: llvm/test/MC/AsmParser/directive_if_offset.s
===================================================================
--- /dev/null
+++ llvm/test/MC/AsmParser/directive_if_offset.s
@@ -0,0 +1,12 @@
+@ RUN: clang -target arm-linux-gnueabihf %s -c -o /dev/null 2>&1 | FileCheck --allow-empty --check-prefix=CHECK-ARM %s
+@ RUN: clang -target thumb-linux-gnueabihf %s -c -o /dev/null 2>&1 | FileCheck --allow-empty --check-prefix=CHECK-THUMB %s
+
+nop
+.arch_extension sec
+9997: nop ;
+.if . - 9997b == 4 ;
+// CHECK-ARM-NOT: :[[@LINE-1]]:5: error: expected absolute expression
+// CHECK-THUMB-NOT: :[[@LINE-2]]:5: error: expected absolute expression
+orr r1, r1, #1 ;
+.else ; orr r1, r1, #2;
+.endif;
Index: llvm/lib/MC/MCExpr.cpp
===================================================================
--- llvm/lib/MC/MCExpr.cpp
+++ llvm/lib/MC/MCExpr.cpp
@@ -524,10 +524,9 @@
   if (!Asm->getWriter().isSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
     return;
 
-  if (SA.getFragment() == SB.getFragment() && !SA.isVariable() &&
-      !SA.isUnset() && !SB.isVariable() && !SB.isUnset()) {
-    Addend += (SA.getOffset() - SB.getOffset());
 
+  auto FinalizeFolding = [&]()
+  {
     // Pointers to Thumb symbols need to have their low-bit set to allow
     // for interworking.
     if (Asm->isThumbFunc(&SA))
@@ -541,16 +540,39 @@
     // Clear the symbol expr pointers to indicate we have folded these
     // operands.
     A = B = nullptr;
+  };
+
+  const MCFragment *FragA = SA.getFragment();
+  const MCFragment *FragB = SB.getFragment();
+  if (FragA == FragB && !SA.isVariable() && !SA.isUnset() && !SB.isVariable() &&
+      !SB.isUnset()) {
+
+    Addend += (SA.getOffset() - SB.getOffset());
+
+    FinalizeFolding();
     return;
   }
 
-  if (!Layout)
+  const MCSection &SecA = *FragA->getParent();
+  const MCSection &SecB = *FragB->getParent();
+
+  if ((&SecA != &SecB) && !Addrs)
     return;
 
-  const MCSection &SecA = *SA.getFragment()->getParent();
-  const MCSection &SecB = *SB.getFragment()->getParent();
+   if ((&SecA != &SecB) && !Addrs)
+     return;
 
-  if ((&SecA != &SecB) && !Addrs)
+   if (SecB.getFragmentList().getNextNode(*FragB) == FragA &&
+       isa<MCDataFragment>(FragA) && isa<MCDataFragment>(FragB)) {
+     Addend +=
+         (SA.getOffset() + (cast<MCDataFragment>(FragB))->getContents().size() -
+          SB.getOffset());
+
+    FinalizeFolding();
+    return;
+  }
+
+  if (!Layout)
     return;
 
   // Eagerly evaluate.
@@ -559,19 +581,7 @@
   if (Addrs && (&SecA != &SecB))
     Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB));
 
-  // Pointers to Thumb symbols need to have their low-bit set to allow
-  // for interworking.
-  if (Asm->isThumbFunc(&SA))
-    Addend |= 1;
-
-  // If symbol is labeled as micromips, we set low-bit to ensure
-  // correct offset in .gcc_except_table
-  if (Asm->getBackend().isMicroMips(&SA))
-    Addend |= 1;
-
-  // Clear the symbol expr pointers to indicate we have folded these
-  // operands.
-  A = B = nullptr;
+  FinalizeFolding();
 }
 
 static bool canFold(const MCAssembler *Asm, const MCSymbolRefExpr *A,


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