[WebAssembly] Make disassembler always emit most canonical name.

Summary:
There are a few instructions that all map to the same opcode, so
when disassembling, we have to pick one. That was just the first one
before (the except_ref variant in the case of "call"), now it is the
one marked as IsCanonical in tablegen, or failing that, the shortest
name (which is typically the "canonical" one).

Also introduced a canonical "end" instruction for this purpose.

Reviewers: dschuff, tlively

Subscribers: sbc100, jgravelle-google, aheejin, llvm-commits, sunfish

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D57713

llvm-svn: 353131

7 files changed, 59 insertions, 20 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrCall.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrCall.td
index a4efa85aadf..6b7c9b24ddc 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrCall.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrCall.td
@@ -93,17 +93,18 @@ let Uses = [SP32, SP64], isCall = 1 in {
   defm "" : SIMD_CALL<v4f32, "v128.">;
   defm "" : SIMD_CALL<v2f64, "v128.">;
 
+  let IsCanonical = 1 in {
   defm CALL_VOID : I<(outs), (ins function32_op:$callee, variable_ops),
-                     (outs), (ins function32_op:$callee),
-                     [(WebAssemblycall0 (i32 imm:$callee))],
-                     "call    \t$callee", "call\t$callee", 0x10>;
+                    (outs), (ins function32_op:$callee),
+                    [(WebAssemblycall0 (i32 imm:$callee))],
+                    "call    \t$callee", "call\t$callee", 0x10>;
 
   let isCodeGenOnly = 1 in {
     defm PCALL_INDIRECT_VOID : I<(outs), (ins I32:$callee, variable_ops),
-                                 (outs), (ins I32:$callee),
-                                 [(WebAssemblycall0 I32:$callee)],
-                                 "PSEUDO CALL INDIRECT\t$callee",
-                                 "PSEUDO CALL INDIRECT\t$callee">;
+                                (outs), (ins I32:$callee),
+                                [(WebAssemblycall0 I32:$callee)],
+                                "PSEUDO CALL INDIRECT\t$callee",
+                                "PSEUDO CALL INDIRECT\t$callee">;
   } // isCodeGenOnly = 1
 
   defm CALL_INDIRECT_VOID : I<(outs),
@@ -113,6 +114,7 @@ let Uses = [SP32, SP64], isCall = 1 in {
                               [],
                               "call_indirect\t", "call_indirect\t$type",
                               0x11>;
+  }
 } // Uses = [SP32,SP64], isCall = 1
 
 // Patterns for matching a direct call to a global address.
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
index 8160cab7520..59faeb88c5e 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
@@ -81,6 +81,10 @@ defm ELSE : NRI<(outs), (ins), [], "else", 0x05>;
 defm END_BLOCK : NRI<(outs), (ins), [], "end_block", 0x0b>;
 defm END_LOOP  : NRI<(outs), (ins), [], "end_loop", 0x0b>;
 defm END_IF    : NRI<(outs), (ins), [], "end_if", 0x0b>;
+// Generic instruction, for disassembler.
+let IsCanonical = 1 in {
+defm END       : NRI<(outs), (ins), [], "end", 0x0b>;
+}
 let isTerminator = 1, isBarrier = 1 in
 defm END_FUNCTION : NRI<(outs), (ins), [], "end_function", 0x0b>;
 } // Uses = [VALUE_STACK], Defs = [VALUE_STACK]
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrFormats.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrFormats.td
index 2a2c79c56d6..aff4d20d8d8 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrFormats.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrFormats.td
@@ -22,6 +22,9 @@ class WebAssemblyInst<bits<32> inst, string asmstr, string stack> : StackRel,
   let Namespace   = "WebAssembly";
   let Pattern     = [];
   let AsmString   = asmstr;
+  // When there are multiple instructions that map to the same encoding (in
+  // e.g. the disassembler use case) prefer the one where IsCanonical == 1.
+  bit IsCanonical = 0;
 }
 
 // Normal instructions. Default instantiation of a WebAssemblyInst.
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
index ab0f48c9a1e..71c469d755b 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
@@ -125,12 +125,14 @@ defm "" : ConstVec<v8i16,
                      ImmI16:$i0, ImmI16:$i1, ImmI16:$i2, ImmI16:$i3,
                      ImmI16:$i4, ImmI16:$i5, ImmI16:$i6, ImmI16:$i7),
                    "$i0, $i1, $i2, $i3, $i4, $i5, $i6, $i7">;
+let IsCanonical = 1 in {
 defm "" : ConstVec<v4i32,
-                   (ins vec_i32imm_op:$i0, vec_i32imm_op:$i1,
+                  (ins vec_i32imm_op:$i0, vec_i32imm_op:$i1,
                         vec_i32imm_op:$i2, vec_i32imm_op:$i3),
-                   (build_vector (i32 imm:$i0), (i32 imm:$i1),
-                                 (i32 imm:$i2), (i32 imm:$i3)),
-                   "$i0, $i1, $i2, $i3">;
+                  (build_vector (i32 imm:$i0), (i32 imm:$i1),
+                                (i32 imm:$i2), (i32 imm:$i3)),
+                  "$i0, $i1, $i2, $i3">;
+}
 defm "" : ConstVec<v2i64,
                    (ins vec_i64imm_op:$i0, vec_i64imm_op:$i1),
                    (build_vector (i64 imm:$i0), (i64 imm:$i1)),
diff --git a/llvm/test/MC/Disassembler/WebAssembly/wasm.txt b/llvm/test/MC/Disassembler/WebAssembly/wasm.txt
index 2632f231cec..8a119fb6b0f 100644
--- a/llvm/test/MC/Disassembler/WebAssembly/wasm.txt
+++ b/llvm/test/MC/Disassembler/WebAssembly/wasm.txt
@@ -22,6 +22,10 @@
 # FIXME: WebAssemblyInstPrinter does not print immediates.
 0x11 0x80 0x01 0x00
 
+# CHECK: call 0
+# CHECK-NOT: except_ref.call 0
+0x10 0x00
+
 # CHECK: local.get 128
 0x20 0x80 0x01
 
@@ -29,8 +33,7 @@
 # CHECK: i64.trunc_sat_f64_u
 0xFC 0x07
 
-# v128.const is arbitrarily disassembled as v16i8
-# CHECK: v128.const 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+# CHECK: v128.const 50462976, 117835012, 185207048, 252579084
 0xFD 0x02 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F
 
 # CHECK: v8x16.shuffle 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
@@ -48,3 +51,7 @@
 # Check br_table, which has its own operand type.
 # CHECK: br_table {0, 1, 2}
 0x0E 0x02 0x00 0x01 0x02
+
+# This can mean end_block/end_loop/end_if/end_function/end_try..
+# CHECK: end
+0x0B
diff --git a/llvm/test/MC/WebAssembly/objdump.s b/llvm/test/MC/WebAssembly/objdump.s
index d156ec60eef..f1cedc7db86 100644
--- a/llvm/test/MC/WebAssembly/objdump.s
+++ b/llvm/test/MC/WebAssembly/objdump.s
@@ -19,8 +19,8 @@ test1:
 # CHECK-LABEL: test0:
 # CHECK-NEXT:        .local  f32, f64, v128, v128
 # CHECK-NEXT:       9:       20 02  local.get	2
-# CHECK-NEXT:       b:       0b     end_block
+# CHECK-NEXT:       b:       0b     end
 # CHECK-LABEL: test1:
 # CHECK-NEXT:        .local  i32, i64, except_ref
 # CHECK-NEXT:      14:       20 03  local.get	3
-# CHECK-NEXT:      16:       0b     end_block
+# CHECK-NEXT:      16:       0b     end
diff --git a/llvm/utils/TableGen/WebAssemblyDisassemblerEmitter.cpp b/llvm/utils/TableGen/WebAssemblyDisassemblerEmitter.cpp
index 249be3b1b95..9f5ae70f836 100644
--- a/llvm/utils/TableGen/WebAssemblyDisassemblerEmitter.cpp
+++ b/llvm/utils/TableGen/WebAssemblyDisassemblerEmitter.cpp
@@ -50,12 +50,33 @@ void emitWebAssemblyDisassemblerTables(
     auto IsStackBased =
         StackString &&
         reinterpret_cast<const StringInit *>(StackString)->getValue() == "true";
-    if (IsStackBased && !CGIP.second) {
-      // this picks the first of many typed variants, which is
-      // currently the except_ref one, though this shouldn't matter for
-      // disassembly purposes.
-      CGIP = std::make_pair(I, &CGI);
+    if (!IsStackBased)
+      continue;
+    if (CGIP.second) {
+      // We already have an instruction for this slot, so decide which one
+      // should be the canonical one. This determines which variant gets
+      // printed in a disassembly. We want e.g. "call" not "i32.call", and
+      // "end" when we don't know if its "end_loop" or "end_block" etc.
+      auto IsCanonicalExisting = CGIP.second->TheDef->getValue("IsCanonical")
+                                     ->getValue()
+                                     ->getAsString() == "1";
+      // We already have one marked explicitly as canonical, so keep it.
+      if (IsCanonicalExisting)
+        continue;
+      auto IsCanonicalNew =
+          Def.getValue("IsCanonical")->getValue()->getAsString() == "1";
+      // If the new one is explicitly marked as canonical, take it.
+      if (!IsCanonicalNew) {
+        // Neither the existing or new instruction is canonical.
+        // Pick the one with with the shortest name as heuristic.
+        // Though ideally IsCanonical is always defined for at least one
+        // variant so this never has to apply.
+        if (CGIP.second->AsmString.size() <= CGI.AsmString.size())
+          continue;
+      }
     }
+    // Set this instruction as the one to use.
+    CGIP = std::make_pair(I, &CGI);
   }
   OS << "#include \"MCTargetDesc/WebAssemblyMCTargetDesc.h\"\n";
   OS << "\n";