[mips] Add support for accessing $gp as a named register.
Summary:
Mips Linux uses $gp to hold a pointer to thread info structure and accesses it
with a named register. This makes this work for LLVM.
The N32 ABI doesn't quite work yet since the frontend generates incorrect IR
for this case. It neglects to truncate the 64-bit GPR to a 32-bit value before
converting to a pointer. Given correct IR (as in the testcase in this patch),
it works correctly.
Reviewers: sstankovic, vmedic, atanasyan
Reviewed By: atanasyan
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D6893
llvm-svn: 225529
diff --git a/llvm/lib/Target/Mips/MipsISelLowering.cpp b/llvm/lib/Target/Mips/MipsISelLowering.cpp
index dfd94ac..99fd739 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.cpp
+++ b/llvm/lib/Target/Mips/MipsISelLowering.cpp
@@ -3839,3 +3839,25 @@
return BB;
}
+
+// FIXME? Maybe this could be a TableGen attribute on some registers and
+// this table could be generated automatically from RegInfo.
+unsigned MipsTargetLowering::getRegisterByName(const char* RegName,
+ EVT VT) const {
+ // Named registers is expected to be fairly rare. For now, just support $28
+ // since the linux kernel uses it.
+ if (Subtarget.isGP64bit()) {
+ unsigned Reg = StringSwitch<unsigned>(RegName)
+ .Case("$28", Mips::GP_64)
+ .Default(0);
+ if (Reg)
+ return Reg;
+ } else {
+ unsigned Reg = StringSwitch<unsigned>(RegName)
+ .Case("$28", Mips::GP)
+ .Default(0);
+ if (Reg)
+ return Reg;
+ }
+ report_fatal_error("Invalid register name global variable");
+}