[WebAssembly] Omit no-op adds for non-mem uses of FrameIndex

llvm/trunk/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp

void WebAssemblyFrameLowering::emitEpilogue(MachineFunction &MF,
   if (InsertPt != MBB.end()) {
     DL = InsertPt->getDebugLoc();
   }
 
   // Restore the stack pointer. Without FP its value is just SP32 - stacksize
   BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg)
       .addImm(StackSize);
   auto *SPSymbol = MF.createExternalSymbolName("__stack_pointer");
+  // TODO: Fold this add into the const offset field of the store.
   BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::ADD_I32), WebAssembly::SP32)
       .addReg(WebAssembly::SP32)
       .addReg(OffsetReg);
   // Re-use OffsetReg to hold the address of the stacktop
   BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg)
       .addExternalSymbol(SPSymbol);
   auto *MMO = new MachineMemOperand(MachinePointerInfo(),
                                     MachineMemOperand::MOStore, 4, 4);
   BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::STORE_I32), WebAssembly::SP32)
       .addImm(0)
       .addReg(OffsetReg)
       .addImm(2) // p2align
       .addReg(WebAssembly::SP32)
       .addMemOperand(MMO);
 }

llvm/trunk/lib/Target/WebAssembly/WebAssemblyPeephole.cpp

for (auto &MI : MBB)
             if (LibInfo.getLibFunc(Name, Func)) {
               const auto &Op2 = MI.getOperand(2);
               if (!Op2.isReg())
                 report_fatal_error("Peephole: call to builtin function with "
                                    "wrong signature, not consuming reg");
               MachineOperand &MO = MI.getOperand(0);
               unsigned OldReg = MO.getReg();
               unsigned NewReg = Op2.getReg();
-              if (MRI.getRegClass(NewReg) != MRI.getRegClass(OldReg))
+
+              // TODO: Handle SP/physregs in MaybeRewriteToDiscard
+              if (TargetRegisterInfo::isVirtualRegister(NewReg) &&
+                  (MRI.getRegClass(NewReg) != MRI.getRegClass(OldReg)))
                 report_fatal_error("Peephole: call to builtin function with "
                                    "wrong signature, from/to mismatch");
               Changed |= MaybeRewriteToDiscard(OldReg, NewReg, MO, MFI, MRI);
             }
           }
         }
       }
       }
 
   return Changed;
 }

llvm/trunk/lib/Target/WebAssembly/WebAssemblyRegisterInfo.cpp

if (MI.mayLoadOrStore()) {
     }
     MI.getOperand(1).setImm(Offset);
     MI.getOperand(2).ChangeToRegister(WebAssembly::SP32, /*IsDef=*/false);
   } else {
     // Otherwise create an i32.add SP, offset and make it the operand.
     auto &MRI = MF.getRegInfo();
     const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
 
-    unsigned OffsetReg = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
+    unsigned FIRegOperand = WebAssembly::SP32;
+    if (FrameOffset) {
+      FIRegOperand = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
       BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(WebAssembly::CONST_I32),
-            OffsetReg)
+              FIRegOperand)
           .addImm(FrameOffset);
       BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(WebAssembly::ADD_I32),
-            OffsetReg)
+              FIRegOperand)
           .addReg(WebAssembly::SP32)
-        .addReg(OffsetReg);
-    MI.getOperand(FIOperandNum).ChangeToRegister(OffsetReg, /*IsDef=*/false);
+          .addReg(FIRegOperand);
+    }
+    MI.getOperand(FIOperandNum).ChangeToRegister(FIRegOperand, /*IsDef=*/false);
   }
 }
 
 unsigned
 WebAssemblyRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
   static const unsigned Regs[2][2] = {
       /*            !isArch64Bit       isArch64Bit      */
       /* !hasFP */ {WebAssembly::SP32, WebAssembly::SP64},

llvm/trunk/test/CodeGen/WebAssembly/mem-intrinsics.ll

 ; CHECK-LABEL: set_no:
 ; CHECK:      i32.call $discard=, memset@FUNCTION, $0, $1, $2{{$}}
 ; CHECK-NEXT: return{{$}}
 define void @set_no(i8* %dst, i8 %src, i32 %len) {
   call void @llvm.memset.p0i8.i32(i8* %dst, i8 %src, i32 %len, i32 1, i1 false)
   ret void
 }
 
+
 ; CHECK-LABEL: frame_index:
 ; CHECK: i32.call $discard=, memset@FUNCTION, $3, $pop1, $pop0{{$}}
+; CHECK: i32.call $discard=, memset@FUNCTION, $4, $pop3, $pop2{{$}}
 ; CHECK: return{{$}}
 define void @frame_index() {
 entry:
   %a = alloca [2048 x i8], align 16
+  %b = alloca [2048 x i8], align 16
   %0 = getelementptr inbounds [2048 x i8], [2048 x i8]* %a, i32 0, i32 0
+  %1 = getelementptr inbounds [2048 x i8], [2048 x i8]* %b, i32 0, i32 0
   call void @llvm.memset.p0i8.i32(i8* %0, i8 256, i32 1024, i32 16, i1 false)
+  call void @llvm.memset.p0i8.i32(i8* %1, i8 256, i32 1024, i32 16, i1 false)
   ret void
 }

llvm/trunk/test/CodeGen/WebAssembly/userstack.ll

 
  ; CHECK-NEXT: i32.const [[L7:.+]]=, 32
  ; CHECK-NEXT: i32.add [[SP]]=, [[SP]], [[L7]]
  ; CHECK-NEXT: i32.const [[L8:.+]]=, __stack_pointer
  ; CHECK-NEXT: i32.store [[SP]]=, 0([[L8]]), [[SP]]
  ret void
 }
 
+declare void @ext_func(i64* %ptr)
+; CHECK-LABEL: non_mem_use
+define void @non_mem_use() {
+ ; CHECK: i32.const [[L2:.+]]=, 16
+ ; CHECK-NEXT: i32.sub [[SP:.+]]=, {{.+}}, [[L2]]
+ %r = alloca i64
+ %r2 = alloca i64
+ ; %r is at SP+8
+ ; CHECK: i32.const [[OFF:.+]]=, 8
+ ; CHECK-NEXT: i32.add [[ARG1:.+]]=, [[SP]], [[OFF]]
+ ; CHECK-NEXT: call ext_func@FUNCTION, [[ARG1]]
+ call void @ext_func(i64* %r)
+ ; %r2 is at SP+0, no add needed
+ ; CHECK-NEXT: call ext_func@FUNCTION, [[SP]]
+ call void @ext_func(i64* %r2)
+ ret void
+}
+
 ; CHECK-LABEL: allocarray_inbounds:
 ; CHECK: .local i32, i32, i32, i32{{$}}
 define void @allocarray_inbounds() {
  ; CHECK: i32.const [[L1:.+]]=, __stack_pointer
  ; CHECK-NEXT: i32.load [[L1]]=, 0([[L1]])
  ; CHECK-NEXT: i32.const [[L2:.+]]=, 32
  ; CHECK-NEXT: i32.sub [[SP:.+]]=, [[L1]], [[L2]]
  %r = alloca [5 x i32]