[llvm] ad0345a - [PowerPC] Emit gnu_attribute according to float-abi metadata

[Qiu Chaofan via llvm-commits]

Author: Qiu Chaofan
Date: 2022-01-26T13:28:50+08:00
New Revision: ad0345aed1e76f98c6ad55372b675c5647e16d28

URL: https://github.com/llvm/llvm-project/commit/ad0345aed1e76f98c6ad55372b675c5647e16d28
DIFF: https://github.com/llvm/llvm-project/commit/ad0345aed1e76f98c6ad55372b675c5647e16d28.diff

LOG: [PowerPC] Emit gnu_attribute according to float-abi metadata

According to GNU as documentation, PowerPC supports some .gnu_attribute
tags to represent the vector and float ABI type in the object file.
Some linkers like GNU ld respects the attribute and will prevent objects
with conflicting ABIs being linked.

This patch emits gnu_attribute value in assembly printer according to
the float-abi metadata. More attributes for soft-fp, hard single/double
and even vector ABI need to be supported in the future.

Reviewed By: jsji

Differential Revision: https://reviews.llvm.org/D117193

Added: 
    llvm/test/CodeGen/PowerPC/gnu-attribute.ll

Modified: 
    llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
index f26c15667a0bb..7809818069965 100644
--- a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -109,6 +109,23 @@ struct DenseMapInfo<std::pair<const MCSymbol *, MCSymbolRefExpr::VariantKind>> {
 
 namespace {
 
+enum {
+  // GNU attribute tags for PowerPC ABI
+  Tag_GNU_Power_ABI_FP = 4,
+  Tag_GNU_Power_ABI_Vector = 8,
+  Tag_GNU_Power_ABI_Struct_Return = 12,
+
+  // GNU attribute values for PowerPC float ABI, as combination of two parts
+  Val_GNU_Power_ABI_NoFloat = 0b00,
+  Val_GNU_Power_ABI_HardFloat_DP = 0b01,
+  Val_GNU_Power_ABI_SoftFloat_DP = 0b10,
+  Val_GNU_Power_ABI_HardFloat_SP = 0b11,
+
+  Val_GNU_Power_ABI_LDBL_IBM128 = 0b0100,
+  Val_GNU_Power_ABI_LDBL_64 = 0b1000,
+  Val_GNU_Power_ABI_LDBL_IEEE128 = 0b1100,
+};
+
 class PPCAsmPrinter : public AsmPrinter {
 protected:
   // For TLS on AIX, we need to be able to identify TOC entries of specific
@@ -178,6 +195,8 @@ class PPCLinuxAsmPrinter : public PPCAsmPrinter {
     return "Linux PPC Assembly Printer";
   }
 
+  void emitGNUAttributes(Module &M);
+
   void emitStartOfAsmFile(Module &M) override;
   void emitEndOfAsmFile(Module &) override;
 
@@ -1388,6 +1407,28 @@ void PPCAsmPrinter::emitInstruction(const MachineInstr *MI) {
   EmitToStreamer(*OutStreamer, TmpInst);
 }
 
+void PPCLinuxAsmPrinter::emitGNUAttributes(Module &M) {
+  // Emit float ABI into GNU attribute
+  Metadata *MD = M.getModuleFlag("float-abi");
+  MDString *FloatABI = dyn_cast_or_null<MDString>(MD);
+  if (!FloatABI)
+    return;
+  StringRef flt = FloatABI->getString();
+  // TODO: Support emitting soft-fp and hard double/single attributes.
+  if (flt == "doubledouble")
+    OutStreamer->emitGNUAttribute(Tag_GNU_Power_ABI_FP,
+                                  Val_GNU_Power_ABI_HardFloat_DP |
+                                      Val_GNU_Power_ABI_LDBL_IBM128);
+  else if (flt == "ieeequad")
+    OutStreamer->emitGNUAttribute(Tag_GNU_Power_ABI_FP,
+                                  Val_GNU_Power_ABI_HardFloat_DP |
+                                      Val_GNU_Power_ABI_LDBL_IEEE128);
+  else if (flt == "ieeedouble")
+    OutStreamer->emitGNUAttribute(Tag_GNU_Power_ABI_FP,
+                                  Val_GNU_Power_ABI_HardFloat_DP |
+                                      Val_GNU_Power_ABI_LDBL_64);
+}
+
 void PPCLinuxAsmPrinter::emitInstruction(const MachineInstr *MI) {
   if (!Subtarget->isPPC64())
     return PPCAsmPrinter::emitInstruction(MI);
@@ -1642,6 +1683,8 @@ void PPCLinuxAsmPrinter::emitEndOfAsmFile(Module &M) {
   PPCTargetStreamer *TS =
       static_cast<PPCTargetStreamer *>(OutStreamer->getTargetStreamer());
 
+  emitGNUAttributes(M);
+
   if (!TOC.empty()) {
     const char *Name = isPPC64 ? ".toc" : ".got2";
     MCSectionELF *Section = OutContext.getELFSection(

diff  --git a/llvm/test/CodeGen/PowerPC/gnu-attribute.ll b/llvm/test/CodeGen/PowerPC/gnu-attribute.ll
new file mode 100644
index 0000000000000..31747146d2345
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/gnu-attribute.ll
@@ -0,0 +1,15 @@
+; RUN: sed -e 's/FLTABI/ieeequad/' %s | llc -mtriple=powerpc64le | FileCheck %s --check-prefix=IEEE
+; RUN: sed -e 's/FLTABI/doubledouble/' %s | llc -mtriple=powerpc64le | FileCheck %s --check-prefix=IBM
+; RUN: sed -e 's/FLTABI/ieeedouble/' %s | llc -mtriple=powerpc64le | FileCheck %s --check-prefix=DBL
+; RUN: sed -e 's/FLTABI//' %s | llc -mtriple=powerpc64le | FileCheck %s --check-prefix=NONE
+
+; IEEE: .gnu_attribute 4, 13
+; IBM: .gnu_attribute 4, 5
+; DBL: .gnu_attribute 4, 9
+; NONE-NOT: .gnu_attribute 4,
+
+!llvm.module.flags = !{!0, !1, !2}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 7, !"uwtable", i32 1}
+!2 = !{i32 1, !"float-abi", !"FLTABI"}