[FPEnv] Allow strict SETCC falling back if strict FP is not supported.

[pengfei]

Summary

This patch fix bug: https://bugs.llvm.org/show_bug.cgi?id=47990

[craig.topper]

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

3772

This assert doesn't do anything. The string is a non-null const char* so the assert will aways pass.

[pengfei]

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

3772

Thanks Craig.

[pengfei]

Address review comment.

[pengfei]

Change to use the common falling back code in line 4964.

[pengfei]

Gently ping.
Although Melanie had a fix D90316 for the initial problem, I think this patch still has value for target during strict FP enabling.

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

if (Legalized) {
 
       Results.push_back(Tmp1);
       if (IsStrict)
         Results.push_back(Chain);
 
       break;
     }
 
-    // FIXME: It seems Legalized is false iff CCCode is Legal. I don't
-    // understand if this code is useful for strict nodes.
-    assert(!IsStrict && "Don't know how to expand for strict nodes.");
+    if (IsStrict) {
+      // FIXME: We may need to add STRICT_FSELECT_CC and STRICT_FSELECT_CCS
+      // handing for target that only supports SELECT_CC.
+      assert(!TLI.isStrictFPEnabled() &&
+             "Expanding to SELECT_CC is not supported for strict nodes.");
+      break;
+    }
 
     // Otherwise, SETCC for the given comparison type must be completely
     // illegal; expand it into a SELECT_CC.
     EVT VT = Node->getValueType(0);
     int TrueValue;
     switch (TLI.getBooleanContents(Tmp1.getValueType())) {
     case TargetLowering::ZeroOrOneBooleanContent:
     case TargetLowering::UndefinedBooleanContent:
       TrueValue = 1;
       break;
     case TargetLowering::ZeroOrNegativeOneBooleanContent:
       TrueValue = -1;
       break;
     }
     Tmp1 = DAG.getNode(ISD::SELECT_CC, dl, VT, Tmp1, Tmp2,
                        DAG.getConstant(TrueValue, dl, VT),
                        DAG.getConstant(0, dl, VT),
                        Tmp3);
     Tmp1->setFlags(Node->getFlags());
     Results.push_back(Tmp1);
     break;
   }
   case ISD::SELECT_CC: {
-    // TODO: need to add STRICT_SELECT_CC and STRICT_SELECT_CCS
+    // TODO: need to add STRICT_FSELECT_CC and STRICT_FSELECT_CCS
     Tmp1 = Node->getOperand(0);   // LHS
     Tmp2 = Node->getOperand(1);   // RHS
     Tmp3 = Node->getOperand(2);   // True
     Tmp4 = Node->getOperand(3);   // False
     EVT VT = Node->getValueType(0);
     SDValue Chain;
     SDValue CC = Node->getOperand(4);
     ISD::CondCode CCOp = cast<CondCodeSDNode>(CC)->get();
if (!Legalized) {
                            Tmp2, Tmp3, Tmp4, CC);
       }
       Tmp1->setFlags(Node->getFlags());
     }
     Results.push_back(Tmp1);
     break;
   }
   case ISD::BR_CC: {
-    // TODO: need to add STRICT_BR_CC and STRICT_BR_CCS
+    // TODO: need to add STRICT_FBR_CC and STRICT_FBR_CCS
     SDValue Chain;
     Tmp1 = Node->getOperand(0);              // Chain
     Tmp2 = Node->getOperand(2);              // LHS
     Tmp3 = Node->getOperand(3);              // RHS
     Tmp4 = Node->getOperand(1);              // CC
 
     bool Legalized =
         LegalizeSetCCCondCode(getSetCCResultType(Tmp2.getValueType()), Tmp2,

llvm/test/CodeGen/WebAssembly/pr47990.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-wasi"
+
+@b = global double 0.000000e+00, align 8
+@a = global double 0.000000e+00, align 8
+
+define i32 @c() nounwind strictfp {
+; CHECK-LABEL: c:
+; CHECK:         .functype c () -> (i32)
+; CHECK-NEXT:  # %bb.0: # %entry
+; CHECK-NEXT:    global.get __stack_pointer
+; CHECK-NEXT:    i32.const 16
+; CHECK-NEXT:    i32.sub
+; CHECK-NEXT:    i32.load 12
+; CHECK-NEXT:    # fallthrough-return
+entry:
+  %retval = alloca i32, align 4
+  %0 = load double, double* @b, align 8
+  %1 = load double, double* @a, align 8
+  %cmp = call i1 @llvm.experimental.constrained.fcmp.f64(double %0, double %1, metadata !"oeq", metadata !"fpexcept.strict") strictfp
+  %conv = zext i1 %cmp to i32
+  %2 = load i32, i32* %retval, align 4
+  ret i32 %2
+}
+
+declare i1 @llvm.experimental.constrained.fcmp.f64(double, double, metadata, metadata) strictfp