[turbofan] phis cannot take registers as inputs

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/704153002

Cr-Commit-Position: refs/heads/master@{#25191}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25191 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/register-allocator.cc

@@ -1525,7 +1525,13 @@ void RegisterAllocator::BuildLiveRanges() {
         for (UsePosition* pos = range->first_pos(); pos != NULL;
              pos = pos->next_) {
           pos->register_beneficial_ = true;
-          pos->requires_reg_ = true;
+          // TODO(dcarney): should the else case assert requires_reg_ == false?
+          // Can't mark phis as needing a register.
+          if (!code()
+                   ->InstructionAt(pos->pos().InstructionIndex())
+                   ->IsGapMoves()) {
+            pos->requires_reg_ = true;
+          }
         }
       }
     }

test/mjsunit/compiler/regress-register-allocator3.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+
+function Module() {
+  "use asm";
+  function f() {
+   var $0 = 0, $25 = 0, $i$014$i = 0, $sum$013$i = 0, $v_0$01$i = 0, $v_1$02$i = 0, $v_10$011$i = 0, $v_11$012$i = 0, $v_2$03$i = 0, $v_3$04$i = 0, $v_4$05$i = 0, $v_5$06$i = 0, $v_6$07$i = 0, $v_7$08$i = 0, $v_8$09$i = 0, $v_9$010$i = 0;
+   $i$014$i = 0;
+   $sum$013$i = 0;
+   $v_0$01$i = 8;
+   $v_1$02$i = 9;
+   $v_10$011$i = 18;
+   $v_11$012$i = 19;
+   $v_2$03$i = 10;
+   $v_3$04$i = 11;
+   $v_4$05$i = 12;
+   $v_5$06$i = 13;
+   $v_6$07$i = 14;
+   $v_7$08$i = 15;
+   $v_8$09$i = 16;
+   $v_9$010$i = 17;
+   do {
+    $v_0$01$i = $v_3$04$i + $v_9$010$i + $v_0$01$i | 0;
+    $v_1$02$i = $v_4$05$i + $v_10$011$i + $v_1$02$i | 0;
+    $v_2$03$i = $v_5$06$i + $v_11$012$i + $v_2$03$i | 0;
+    $v_3$04$i = $v_3$04$i + $v_6$07$i + $v_0$01$i | 0;
+    $v_4$05$i = $v_4$05$i + $v_7$08$i + $v_1$02$i | 0;
+    $v_5$06$i = $v_5$06$i + $v_8$09$i + $v_2$03$i | 0;
+    $v_6$07$i = $v_6$07$i + $v_9$010$i + $v_3$04$i | 0;
+    $v_7$08$i = $v_7$08$i + $v_10$011$i + $v_4$05$i | 0;
+    $v_8$09$i = $v_8$09$i + $v_11$012$i + $v_5$06$i | 0;
+    $v_9$010$i = $v_0$01$i + $v_9$010$i + $v_6$07$i | 0;
+    $v_10$011$i = $v_1$02$i + $v_10$011$i + $v_7$08$i | 0;
+    $v_11$012$i = $v_2$03$i + $v_11$012$i + $v_8$09$i | 0;
+    $25 = $v_0$01$i + $v_1$02$i | 0;
+    $sum$013$i = $v_2$03$i + $sum$013$i + $v_5$06$i + $v_4$05$i + $v_8$09$i + $v_3$04$i + $25 + $v_7$08$i + $v_11$012$i + $v_6$07$i + $v_10$011$i + $v_9$010$i | 0;
+    $i$014$i = $i$014$i + 1 | 0;
+   } while (($i$014$i | 0) <= 0);
+   return $sum$013$i - ($v_5$06$i + $v_2$03$i + $v_4$05$i + $v_8$09$i + $25 + $v_3$04$i + $v_7$08$i + $v_11$012$i + $v_6$07$i + $v_10$011$i + $v_9$010$i);
+  }
+  return { f: f };
+}
+
+Module().f();

test/unittests/compiler/register-allocator-unittest.cc

@@ -453,6 +453,61 @@ TEST_F(RegisterAllocatorTest, SimpleBranch) {
   Allocate();
 }
 
+
+TEST_F(RegisterAllocatorTest, RegressionPhisNeedTooManyRegisters) {
+  const size_t kNumRegs = 3;
+  const size_t kParams = kNumRegs + 1;
+  int parameters[kParams];
+
+  // Override number of registers.
+  SetNumRegs(kNumRegs, kNumRegs);
+
+  // Initial block.
+  StartBlock();
+  int constant = DefineConstant();
+  for (size_t i = 0; i < arraysize(parameters); ++i) {
+    parameters[i] = DefineConstant();
+  }
+  EndBlock();
+
+  PhiInstruction* phis[kParams];
+  {
+    StartLoop(2);
+
+    // Loop header.
+    StartBlock();
+
+    for (size_t i = 0; i < arraysize(parameters); ++i) {
+      phis[i] = Phi(parameters[i]);
+    }
+
+    // Perform some computations.
+    // something like phi[i] += const
+    for (size_t i = 0; i < arraysize(parameters); ++i) {
+      int result = NewReg();
+      EmitFRU(result, phis[i]->virtual_register(), constant);
+      phis[i]->operands().push_back(result);
+    }
+
+    EndBlock(Branch(DefineConstant(), 1, 2));
+
+    // Jump back to loop header.
+    StartBlock();
+    EndBlock(Jump(-1));
+
+    EndLoop();
+  }
+
+  // End block.
+  StartLastBlock();
+
+  // Return sum.
+  Return(DefineConstant());
+  EndBlock();
+
+  Allocate();
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8