[RISCV] Support -target-abi at the MC layer and for codegen

This patch adds proper handling of -target-abi, as accepted by llvm-mc and
llc. Lowering (codegen) for the hard-float ABIs will follow in a subsequent
patch. However, this patch does add MC layer support for the hard float and
RVE ABIs (emission of the appropriate ELF flags
https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#-file-header).

ABI parsing must be shared between codegen and the MC layer, so we add
computeTargetABI to RISCVUtils. A warning will be printed if an invalid or
unrecognized ABI is given.

Differential Revision: https://reviews.llvm.org/D59023

llvm-svn: 355771

1 files changed, 51 insertions, 0 deletions

diff --git a/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.cpp b/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.cpp
index 964af1f74ce..bb967cb0248 100644
--- a/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.cpp
+++ b/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.cpp
@@ -1,9 +1,60 @@
 #include "RISCVBaseInfo.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Support/raw_ostream.h"
 
 namespace llvm {
 namespace RISCVSysReg {
 #define GET_SysRegsList_IMPL
 #include "RISCVGenSystemOperands.inc"
 } // namespace RISCVSysReg
+
+namespace RISCVABI {
+ABI computeTargetABI(const Triple &TT, FeatureBitset FeatureBits,
+                     StringRef ABIName) {
+  auto TargetABI = StringSwitch<ABI>(ABIName)
+                       .Case("ilp32", ABI_ILP32)
+                       .Case("ilp32f", ABI_ILP32F)
+                       .Case("ilp32d", ABI_ILP32D)
+                       .Case("ilp32e", ABI_ILP32E)
+                       .Case("lp64", ABI_LP64)
+                       .Case("lp64f", ABI_LP64F)
+                       .Case("lp64d", ABI_LP64D)
+                       .Default(ABI_Unknown);
+
+  if (!ABIName.empty() && TargetABI == ABI_Unknown) {
+    errs()
+        << "'" << ABIName
+        << "' is not a recognized ABI for this target (ignoring target-abi)\n";
+  } else if (ABIName.startswith("ilp32") && TT.isArch64Bit()) {
+    errs() << "32-bit ABIs are not supported for 64-bit targets (ignoring "
+              "target-abi)\n";
+    TargetABI = ABI_Unknown;
+  } else if (ABIName.startswith("lp64") && !TT.isArch64Bit()) {
+    errs() << "64-bit ABIs are not supported for 32-bit targets (ignoring "
+              "target-abi)\n";
+    TargetABI = ABI_Unknown;
+  } else if (ABIName.endswith("f") && !FeatureBits[RISCV::FeatureStdExtF]) {
+    errs() << "Hard-float 'f' ABI can't be used for a target that "
+              "doesn't support the F instruction set extension (ignoring "
+              "target-abi)\n";
+    TargetABI = ABI_Unknown;
+  } else if (ABIName.endswith("d") && !FeatureBits[RISCV::FeatureStdExtD]) {
+    errs() << "Hard-float 'd' ABI can't be used for a target that "
+              "doesn't support the D instruction set extension (ignoring "
+              "target-abi)\n";
+    TargetABI = ABI_Unknown;
+  }
+
+  // For now, default to the ilp32/lp64 if no explicit ABI is given or an
+  // invalid/unrecognised string is given. In the future, it might be worth
+  // changing this to default to ilp32f/lp64f and ilp32d/lp64d when hardware
+  // support for floating point is present.
+  if (TargetABI == ABI_Unknown) {
+    TargetABI = TT.isArch64Bit() ? ABI_LP64 : ABI_ILP32;
+  }
+
+  return TargetABI;
+}
+} // namespace RISCVABI
 } // namespace llvm