[PATCH] D69411: [MC] Calculate difference of symbols in two fragments when possible
Jian Cai via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 24 15:03:51 PDT 2019
jcai19 created this revision.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.
Parse .if directive substracting dot symbol to a label right before,
when they are assgiend to two different MCFragments and both fragments
are not relaxable, e.g. 9997: inst ; .if . - 9997b == 2.
https://bugs.llvm.org/show_bug.cgi?id=43795
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D69411
Files:
llvm/lib/MC/MCExpr.cpp
Index: llvm/lib/MC/MCExpr.cpp
===================================================================
--- llvm/lib/MC/MCExpr.cpp
+++ llvm/lib/MC/MCExpr.cpp
@@ -513,6 +513,8 @@
const MCSymbol &SA = A->getSymbol();
const MCSymbol &SB = B->getSymbol();
+ const MCFragment *FragA = SA.getFragment();
+ const MCFragment *FragB = SB.getFragment();
if (SA.isUndefined() || SB.isUndefined())
return;
@@ -520,8 +522,9 @@
if (!Asm->getWriter().isSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
return;
- if (SA.getFragment() == SB.getFragment() && !SA.isVariable() &&
- !SA.isUnset() && !SB.isVariable() && !SB.isUnset()) {
+ if (FragA == FragB && !SA.isVariable() && !SA.isUnset() && !SB.isVariable() &&
+ !SB.isUnset()) {
+
Addend += (SA.getOffset() - SB.getOffset());
// Pointers to Thumb symbols need to have their low-bit set to allow
@@ -540,13 +543,39 @@
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();
+ // Pointers to Thumb symbols need to have their low-bit set to allow
+ if ((&SecA != &SecB) && !Addrs)
+ return;
- if ((&SecA != &SecB) && !Addrs)
+ if (SecB.getFragmentList().getNextNode(*FragB) == FragA &&
+ dyn_cast<MCDataFragment>(FragA) && dyn_cast<MCDataFragment>(FragB)) {
+ Addend +=
+ (SA.getOffset() + (cast<MCDataFragment>(FragB))->getContents().size() -
+ SB.getOffset());
+
+ // 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;
+ return;
+ }
+
+ if (!Layout)
return;
// Eagerly evaluate.
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