[llvm-mca] Propagate fatal llvm-mca errors from library classes to driver.

Summary:
This patch introduces error handling to propagate the errors from llvm-mca library classes (or what will become library classes) up to the driver.  This patch also introduces an enum to make clearer the intention of the return value for Stage::execute.

This supports PR38101.

Reviewers: andreadb, courbet, RKSimon

Reviewed By: andreadb

Subscribers: llvm-commits, tschuett, gbedwell

Differential Revision: https://reviews.llvm.org/D50561

llvm-svn: 339594

1 files changed, 8 insertions, 2 deletions

diff --git a/llvm/tools/llvm-mca/RegisterFile.cpp b/llvm/tools/llvm-mca/RegisterFile.cpp
index 44de105b899..ea27a8b9b68 100644
--- a/llvm/tools/llvm-mca/RegisterFile.cpp
+++ b/llvm/tools/llvm-mca/RegisterFile.cpp
@@ -306,8 +306,14 @@ unsigned RegisterFile::isAvailable(ArrayRef<unsigned> Regs) const {
       // microarchitectural registers in register file #0 was changed by the
       // users via flag -reg-file-size. Alternatively, the scheduling model
       // specified a too small number of registers for this register file.
-      report_fatal_error(
-          "Not enough microarchitectural registers in the register file");
+      LLVM_DEBUG(dbgs() << "Not enough registers in the register file.\n");
+
+      // FIXME: Normalize the instruction register count to match the
+      // NumPhysRegs value.  This is a highly unusual case, and is not expected
+      // to occur.  This normalization is hiding an inconsistency in either the
+      // scheduling model or in the value that the user might have specified
+      // for NumPhysRegs.
+      NumRegs = RMT.NumPhysRegs;
     }
 
     if (RMT.NumPhysRegs < (RMT.NumUsedPhysRegs + NumRegs))