[WebAssembly] Fix printing of global operands

[dschuff]

Summary

They still need to be printed as "i32.const" rather than "global".
(Fixed from r252656 which wasn't quite NFC)

[sunfish]

Actually, I believe there's a better way to fix this. X86 uses this, for example:

def : Pat<(i32 (X86Wrapper tglobaladdr :$dst)), (MOV32ri tglobaladdr :$dst)>;

We should be able to replace our GLOBAL instruction with essentially the same thing (our version of MOV32ri is just Const_I32). This will use i32.const instructions right from the start, so they should then go down the normal path in the assembly printer.

[dschuff]

• Use a pattern instead of a custom instruction

[jfb]

lgtm

llvm/trunk/lib/Target/WebAssembly/WebAssemblyInstrInfo.td

def CONST_I64 : I<(outs I64:$res), (ins i64imm:$imm),
                   "i64.const\t$res, $imm">;
 def CONST_F32 : I<(outs F32:$res), (ins f32imm:$imm),
                   [(set F32:$res, fpimm:$imm)],
                   "f32.const\t$res, $imm">;
 def CONST_F64 : I<(outs F64:$res), (ins f64imm:$imm),
                   [(set F64:$res, fpimm:$imm)],
                   "f64.const\t$res, $imm">;
 
-// Special types of immediates. FIXME: Hard-coded as 32-bit for now.
-def GLOBAL : I<(outs I32:$dst), (ins global:$addr),
-               [(set I32:$dst, (WebAssemblywrapper tglobaladdr:$addr))],
-               "global\t$dst, $addr">;
+
+def : Pat<(i32 (WebAssemblywrapper tglobaladdr :$dst)),
+          (CONST_I32 tglobaladdr :$dst)>;
+
 def JUMP_TABLE : I<(outs I32:$dst), (ins tjumptable_op:$addr),
                    [(set I32:$dst, (WebAssemblywrapper tjumptable:$addr))],
                    "jump_table\t$dst, $addr">;
 
 //===----------------------------------------------------------------------===//
 // Additional sets of instructions.
 //===----------------------------------------------------------------------===//
 
 include "WebAssemblyInstrMemory.td"
 include "WebAssemblyInstrCall.td"
 include "WebAssemblyInstrControl.td"
 include "WebAssemblyInstrInteger.td"
 include "WebAssemblyInstrFloat.td"
 include "WebAssemblyInstrConv.td"
 include "WebAssemblyInstrAtomics.td"
 include "WebAssemblyInstrSIMD.td"

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

 ; RUN: llc < %s -asm-verbose=false | FileCheck %s
 
 ; Test that globals assemble as expected.
 
 target datalayout = "e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown"
 
 ; CHECK-NOT: llvm.used
 ; CHECK-NOT: llvm.metadata
 @llvm.used = appending global [1 x i32*] [i32* @g], section "llvm.metadata"
 
+; CHECK: foo:
+; CHECK: i32.const $push, answer
+define i32 @foo() {
+  %a = load i32, i32* @answer
+  ret i32 %a
+}
+
 ; CHECK: .type   g,@object
 ; CHECK: .align  2{{$}}
 ; CHECK-NEXT: g:
 ; CHECK-NEXT: .int32 1337{{$}}
 ; CHECK-NEXT: .size g, 4{{$}}
 @g = private global i32 1337
 
 ; CHECK-LABEL: ud: