Fix the asmprinter so that a globalvalue can specify an explicit alignment
smaller than the preferred alignment, but so that the target can actually
specify a minimum alignment if needed. This fixes some objc protocol
failures Devang tracked down.
llvm-svn: 37373
diff --git a/llvm/lib/CodeGen/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter.cpp
index fd112a3..07319d5 100644
--- a/llvm/lib/CodeGen/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter.cpp
@@ -605,12 +605,25 @@
//===----------------------------------------------------------------------===//
-// EmitAlignment - Emit an alignment directive to the specified power of two.
-// Use the maximum of the specified alignment and the alignment from the
-// specified GlobalValue (if any).
-void AsmPrinter::EmitAlignment(unsigned NumBits, const GlobalValue *GV) const {
+// EmitAlignment - Emit an alignment directive to the specified power of
+// two boundary. For example, if you pass in 3 here, you will get an 8
+// byte alignment. If a global value is specified, and if that global has
+// an explicit alignment requested, it will unconditionally override the
+// alignment request. However, if ForcedAlignBits is specified, this value
+// has final say: the ultimate alignment will be the max of ForcedAlignBits
+// and the alignment computed with NumBits and the global.
+//
+// The algorithm is:
+// Align = NumBits;
+// if (GV && GV->hasalignment) Align = GV->getalignment();
+// Align = std::max(Align, ForcedAlignBits);
+//
+void AsmPrinter::EmitAlignment(unsigned NumBits, const GlobalValue *GV,
+ unsigned ForcedAlignBits) const {
if (GV && GV->getAlignment())
- NumBits = std::max(NumBits, Log2_32(GV->getAlignment()));
+ NumBits = Log2_32(GV->getAlignment());
+ NumBits = std::max(NumBits, ForcedAlignBits);
+
if (NumBits == 0) return; // No need to emit alignment.
if (TAI->getAlignmentIsInBytes()) NumBits = 1 << NumBits;
O << TAI->getAlignDirective() << NumBits << "\n";