[llvm] r205601 - [RegAllocGreedy][Last Chance Recoloring] Emit diagnostics when last chance

[Quentin Colombet]

Author: qcolombet
Date: Thu Apr  3 21:05:21 2014
New Revision: 205601

URL: http://llvm.org/viewvc/llvm-project?rev=205601&view=rev
Log:
[RegAllocGreedy][Last Chance Recoloring] Emit diagnostics when last chance
recoloring cut-offs are encountered and register allocation failed.

This is related to PR18747

Patch by MAYUR PANDEY <mayur.p at samsung.com>.

Modified:
    llvm/trunk/lib/CodeGen/RegAllocGreedy.cpp
    llvm/trunk/test/CodeGen/X86/ragreedy-last-chance-recoloring.ll

Modified: llvm/trunk/lib/CodeGen/RegAllocGreedy.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegAllocGreedy.cpp?rev=205601&r1=205600&r2=205601&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegAllocGreedy.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegAllocGreedy.cpp Thu Apr  3 21:05:21 2014
@@ -37,6 +37,7 @@
 #include "llvm/CodeGen/RegAllocRegistry.h"
 #include "llvm/CodeGen/RegisterClassInfo.h"
 #include "llvm/CodeGen/VirtRegMap.h"
+#include "llvm/IR/LLVMContext.h"
 #include "llvm/PassAnalysisSupport.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
@@ -147,6 +148,22 @@ class RAGreedy : public MachineFunctionP
     RS_Done
   };
 
+  // Enum CutOffStage to keep a track whether the register allocation failed
+  // because of the cutoffs encountered in last chance recoloring.
+  // Note: This is used as bitmask. New value should be next power of 2.
+  enum CutOffStage {
+    // No cutoffs encountered
+    CO_None = 0,
+
+    // lcr-max-depth cutoff encountered
+    CO_Depth = 1,
+
+    // lcr-max-interf cutoff encountered
+    CO_Interf = 2
+  };
+
+  uint8_t CutOffInfo;
+
 #ifndef NDEBUG
   static const char *const StageName[];
 #endif
@@ -1912,6 +1929,7 @@ RAGreedy::mayRecolorAllInterferences(uns
     if (Q.collectInterferingVRegs(LastChanceRecoloringMaxInterference) >=
         LastChanceRecoloringMaxInterference) {
       DEBUG(dbgs() << "Early abort: too many interferences.\n");
+      CutOffInfo |= CO_Interf;
       return false;
     }
     for (unsigned i = Q.interferingVRegs().size(); i; --i) {
@@ -1984,6 +2002,7 @@ unsigned RAGreedy::tryLastChanceRecolori
   // Indeed, in that case we may want to cut the search space earlier.
   if (Depth >= LastChanceRecoloringMaxDepth) {
     DEBUG(dbgs() << "Abort because max depth has been reached.\n");
+    CutOffInfo |= CO_Depth;
     return ~0u;
   }
 
@@ -2108,8 +2127,23 @@ bool RAGreedy::tryRecoloringCandidates(P
 
 unsigned RAGreedy::selectOrSplit(LiveInterval &VirtReg,
                                  SmallVectorImpl<unsigned> &NewVRegs) {
+  CutOffInfo = CO_None;
+  LLVMContext &Ctx = MF->getFunction()->getContext();
   SmallVirtRegSet FixedRegisters;
-  return selectOrSplitImpl(VirtReg, NewVRegs, FixedRegisters);
+  unsigned Reg = selectOrSplitImpl(VirtReg, NewVRegs, FixedRegisters);
+  if (Reg == ~0U && (CutOffInfo != CO_None)) {
+    uint8_t CutOffEncountered = CutOffInfo & (CO_Depth | CO_Interf);
+    if (CutOffEncountered == CO_Depth)
+      Ctx.emitError(
+          "register allocation failed: maximum depth for recoloring reached");
+    else if (CutOffEncountered == CO_Interf)
+      Ctx.emitError("register allocation failed: maximum interference for "
+                    "recoloring reached");
+    else if (CutOffEncountered == (CO_Depth | CO_Interf))
+      Ctx.emitError("register allocation failed: maximum interference and "
+                    "depth for recoloring reached");
+  }
+  return Reg;
 }
 
 /// Using a CSR for the first time has a cost because it causes push|pop

Modified: llvm/trunk/test/CodeGen/X86/ragreedy-last-chance-recoloring.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/ragreedy-last-chance-recoloring.ll?rev=205601&r1=205600&r2=205601&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/ragreedy-last-chance-recoloring.ll (original)
+++ llvm/trunk/test/CodeGen/X86/ragreedy-last-chance-recoloring.ll Thu Apr  3 21:05:21 2014
@@ -2,6 +2,12 @@
 ; Without the last chance recoloring, this test fails with:
 ; "ran out of registers".
 
+; RUN: not llc -regalloc=greedy -relocation-model=pic -lcr-max-depth=0  < %s 2>&1 | FileCheck %s --check-prefix=CHECK-DEPTH
+; Test whether failure due to cutoff for depth is reported
+
+; RUN: not llc -regalloc=greedy -relocation-model=pic -lcr-max-interf=1  < %s 2>&1 | FileCheck %s --check-prefix=CHECK-INTERF
+; Test whether failure due to cutoff for interference is reported
+
 target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32-S128"
 target triple = "i386-apple-macosx"
 
@@ -12,6 +18,8 @@ target triple = "i386-apple-macosx"
 
 ; Function Attrs: nounwind ssp
 ; CHECK-NOT: ran out of registers during register allocation
+; CHECK-INTERF: error: register allocation failed: maximum interference for recoloring reached
+; CHECK-DEPTH: error: register allocation failed: maximum depth for recoloring reached
 define void @fp_dh_f870bf31fd8ffe068450366e3f05389a(i8* %arg) #0 {
 bb:
   indirectbr i8* undef, [label %bb85, label %bb206]