[WebAssembly] Implement prolog/epilog insertion and FrameIndex elimination

Summary:
Use the SP32 physical register as the base for FrameIndex
lowering. Update it and the __stack_pointer global var in the prolog and
epilog. Extend the mapping of virtual registers to wasm locals to
include the physical registers.

Rather than modify the target-independent PrologEpilogInserter (which
asserts that there are no virtual registers left) include a
slightly-modified copy for Wasm that does not have this assertion and
only clears the virtual registers if scavenging was needed (which of
course it isn't for wasm).

Differential Revision: http://reviews.llvm.org/D15344

llvm-svn: 255392

1 files changed, 19 insertions, 4 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h b/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h
index af4dabb2c6c..e3c7f41189b 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h
@@ -16,6 +16,7 @@
 #ifndef LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYMACHINEFUNCTIONINFO_H
 #define LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYMACHINEFUNCTIONINFO_H
 
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 
 namespace llvm {
@@ -38,8 +39,13 @@ class WebAssemblyFunctionInfo final : public MachineFunctionInfo {
   ///   - defined and used in LIFO order with other stack registers
   BitVector VRegStackified;
 
+  // One entry for each possible target reg. we expect it to be small.
+  std::vector<unsigned> PhysRegs;
+
 public:
-  explicit WebAssemblyFunctionInfo(MachineFunction &MF) : MF(MF) {}
+  explicit WebAssemblyFunctionInfo(MachineFunction &MF) : MF(MF) {
+    PhysRegs.resize(WebAssembly::NUM_TARGET_REGS, -1U);
+  }
   ~WebAssemblyFunctionInfo() override;
 
   void addParam(MVT VT) { Params.push_back(VT); }
@@ -64,9 +70,12 @@ public:
     assert(TargetRegisterInfo::virtReg2Index(VReg) < WARegs.size());
     WARegs[TargetRegisterInfo::virtReg2Index(VReg)] = WAReg;
   }
-  unsigned getWAReg(unsigned VReg) const {
-    assert(TargetRegisterInfo::virtReg2Index(VReg) < WARegs.size());
-    return WARegs[TargetRegisterInfo::virtReg2Index(VReg)];
+  unsigned getWAReg(unsigned Reg) const {
+    if (TargetRegisterInfo::isVirtualRegister(Reg)) {
+      assert(TargetRegisterInfo::virtReg2Index(Reg) < WARegs.size());
+      return WARegs[TargetRegisterInfo::virtReg2Index(Reg)];
+    }
+    return PhysRegs[Reg];
   }
   // If new virtual registers are created after initWARegs has been called,
   // this function can be used to add WebAssembly register mappings for them.
@@ -74,6 +83,12 @@ public:
     assert(VReg = WARegs.size());
     WARegs.push_back(WAReg);
   }
+
+  void addPReg(unsigned PReg, unsigned WAReg) {
+    assert(PReg < WebAssembly::NUM_TARGET_REGS);
+    assert(WAReg < -1U);
+    PhysRegs[PReg] = WAReg;
+  }
 };
 
 } // end namespace llvm