[WebAssembly] Don't assume that zext/sext result is i32/i64 in fast isel (PR41841)

[nikic]

Summary

Usually this will abort fast-isel at the instruction using the non-legal result, but if the only use is in a different basic block, we'll incorrectly assume that the zext/sext is to i32 (rather than i128 in this case).

[tlively]

Thanks for fixing this! I have a few comments on the test style, but otherwise LGTM.

llvm/test/CodeGen/WebAssembly/PR41841.ll

1 ↗

(On Diff #199134)

We usually pass -asm-verbose=false in our tests to avoid having to match uninteresting output.

18 ↗

(On Diff #199134)

Please move the CHECK lines to be right before the top of the function

36 ↗

(On Diff #199134)

Please standardize the whitespace to make the start of the instructions line up.

[nikic]

Add -asm-verbose=false, move CHECK lines, remove tabs.

[tlively]

Looks good. Feel free to commit yourself or lmk if you want me to commit it for you.

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

if (To == MVT::i64) {
 
     unsigned Result = createResultReg(&WebAssembly::I64RegClass);
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
             TII.get(WebAssembly::I64_EXTEND_U_I32), Result)
         .addReg(Reg);
     return Result;
   }
 
+  if (To == MVT::i32)
     return zeroExtendToI32(Reg, V, From);
+
+  return 0;
 }
 
 unsigned WebAssemblyFastISel::signExtend(unsigned Reg, const Value *V,
                                          MVT::SimpleValueType From,
                                          MVT::SimpleValueType To) {
   if (To == MVT::i64) {
     if (From == MVT::i64)
       return copyValue(Reg);
 
     Reg = signExtendToI32(Reg, V, From);
 
     unsigned Result = createResultReg(&WebAssembly::I64RegClass);
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
             TII.get(WebAssembly::I64_EXTEND_S_I32), Result)
         .addReg(Reg);
     return Result;
   }
 
+  if (To == MVT::i32)
     return signExtendToI32(Reg, V, From);
+
+  return 0;
 }
 
 unsigned WebAssemblyFastISel::getRegForUnsignedValue(const Value *V) {
   MVT::SimpleValueType From = getSimpleType(V->getType());
   MVT::SimpleValueType To = getLegalType(From);
   unsigned VReg = getRegForValue(V);
   if (VReg == 0)
     return 0;

llvm/trunk/test/CodeGen/WebAssembly/PR41841.ll

+; RUN: llc < %s -O0 -wasm-disable-explicit-locals -wasm-keep-registers -asm-verbose=false | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+declare void @foo(i128)
+
+; CHECK-LABEL: test_zext:
+; CHECK-NEXT: .functype test_zext (i32) -> (){{$}}
+; CHECK-NEXT: i64.extend_i32_u $[[TMP3:[0-9]+]]=, $0{{$}}
+; CHECK-NEXT: i64.const $[[TMP4:[0-9]+]]=, 1{{$}}
+; CHECK-NEXT: i64.and $[[TMP1:[0-9]+]]=, $[[TMP3]], $[[TMP4]]{{$}}
+; CHECK-NEXT: i64.const $[[TMP2:[0-9]+]]=, 0{{$}}
+; CHECK-NEXT: call foo, $[[TMP1]], $[[TMP2]]{{$}}
+; CHECK-NEXT: return{{$}}
+define void @test_zext(i1 %b) nounwind {
+  %res = zext i1 %b to i128
+  br label %next
+
+next:                                             ; preds = %start
+  call void @foo(i128 %res)
+  ret void
+}
+
+; CHECK-LABEL: test_sext:
+; CHECK-NEXT:.functype test_sext (i32) -> (){{$}}
+; CHECK-NEXT: i64.extend_i32_u $[[TMP3:[0-9]+]]=, $0{{$}}
+; CHECK-NEXT: i64.const $[[TMP4:[0-9]+]]=, 1{{$}}
+; CHECK-NEXT: i64.and $[[TMP5:[0-9]+]]=, $[[TMP3]], $[[TMP4]]{{$}}
+; CHECK-NEXT: i64.const $[[TMP6:[0-9]+]]=, 0{{$}}
+; CHECK-NEXT: i64.sub $[[TMP1:[0-9]+]]=, $[[TMP6]], $[[TMP5]]{{$}}
+; CHECK-NEXT: local.copy $[[TMP2:[0-9]+]]=, $[[TMP1]]{{$}}
+; CHECK-NEXT: call foo, $[[TMP1]], $[[TMP2]]{{$}}
+; CHECK-NEXT: return{{$}}
+define void @test_sext(i1 %b) nounwind {
+  %res = sext i1 %b to i128
+  br label %next
+
+next:                                             ; preds = %start
+  call void @foo(i128 %res)
+  ret void
+}