Fix an issue where we were reusing materializations of constants in blocks not domina...

the simple fix, materializing the constant before every use.  It might be better to either track domination of uses or
to materialize all constants and the beginning of the function and let remat sort when to do materialization at uses.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55703 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index e44a6c29f55a1fa21c3e29f305dc9369a182d2d3..6b47e1808f0938fbeb4ecf70029e150409d237b1 100644 (file)
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -21,21 +21,26 @@
 #include "llvm/Target/TargetMachine.h"
 using namespace llvm;
 
+// Don't cache constant materializations.  To do so would require
+// tracking what uses they dominate.  Non-constants, however, already
+// have the SSA def-doms-use requirement enforced, so we can cache their
+// computations.
 unsigned FastISel::getRegForValue(Value *V,
                                   DenseMap<const Value*, unsigned> &ValueMap) {
-  unsigned &Reg = ValueMap[V];
-  if (Reg != 0)
-    return Reg;
+  if (ValueMap.count(V))
+    return ValueMap[V];
 
   MVT::SimpleValueType VT = TLI.getValueType(V->getType()).getSimpleVT();
   if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
     if (CI->getValue().getActiveBits() > 64)
       return 0;
-    Reg = FastEmit_i(VT, VT, ISD::Constant, CI->getZExtValue());
+    // Don't cache constant materializations.  To do so would require
+    // tracking what uses they dominate.
+    return FastEmit_i(VT, VT, ISD::Constant, CI->getZExtValue());
   } else if (isa<ConstantPointerNull>(V)) {
-    Reg = FastEmit_i(VT, VT, ISD::Constant, 0);
+    return FastEmit_i(VT, VT, ISD::Constant, 0);
   } else if (ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
-    Reg = FastEmit_f(VT, VT, ISD::ConstantFP, CF);
+    unsigned Reg = FastEmit_f(VT, VT, ISD::ConstantFP, CF);
 
     if (!Reg) {
       const APFloat &Flt = CF->getValueAPF();
@@ -56,12 +61,13 @@ unsigned FastISel::getRegForValue(Value *V,
       if (Reg == 0)
         return 0;
     }
+    
+    return Reg;
   } else if (isa<UndefValue>(V)) {
-    Reg = createResultReg(TLI.getRegClassFor(VT));
+    unsigned Reg = createResultReg(TLI.getRegClassFor(VT));
     BuildMI(MBB, TII.get(TargetInstrInfo::IMPLICIT_DEF), Reg);
+    return Reg;
   }
-
-  return Reg;
 }
 
 /// UpdateValueMap - Update the value map to include the new mapping for this