[RegAlloc] Avoid compile time regression with multiple copy hints.

As a fix for https://bugs.llvm.org/show_bug.cgi?id=40986 ("excessive compile time building opencollada"), this patch makes sure that no phys reg is hinted more than once from getRegAllocationHints(). This handles the case were many virtual registers are assigned to the same physreg. The previous compile time fix (r343686) in weightCalcHelper() only made sure that physical/virtual registers are passed no more than once to addRegAllocationHint(). Review: Dimitry Andric, Quentin Colombet https://reviews.llvm.org/D59201 llvm-svn: 355854
llvm · Mar 11, 2019 · 8b8dc50 · 8b8dc50
1 parent 20e7c0c
commit 8b8dc50
Showing 2 changed files with 811 additions and 0 deletions.
diff --git a/llvm/lib/CodeGen/TargetRegisterInfo.cpp b/llvm/lib/CodeGen/TargetRegisterInfo.cpp
@@ -13,6 +13,7 @@
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
@@ -397,6 +398,7 @@ TargetRegisterInfo::getRegAllocationHints(unsigned VirtReg,
   const std::pair<unsigned, SmallVector<unsigned, 4>> &Hints_MRI =
     MRI.getRegAllocationHints(VirtReg);
 
+  SmallSet<unsigned, 32> HintedRegs;
   // First hint may be a target hint.
   bool Skip = (Hints_MRI.first != 0);
   for (auto Reg : Hints_MRI.second) {
@@ -410,6 +412,10 @@ TargetRegisterInfo::getRegAllocationHints(unsigned VirtReg,
     if (VRM && isVirtualRegister(Phys))
       Phys = VRM->getPhys(Phys);
 
+    // Don't add the same reg twice (Hints_MRI may contain multiple virtual
+    // registers allocated to the same physreg).
+    if (!HintedRegs.insert(Phys).second)
+      continue;
     // Check that Phys is a valid hint in VirtReg's register class.
     if (!isPhysicalRegister(Phys))
       continue;