[llvm] r323582 - [GlobalISel][Legalizer] Convert the FP constants to the right APFloat type for G_FCONSTANT.

[Amara Emerson via llvm-commits]

Author: aemerson
Date: Fri Jan 26 23:07:20 2018
New Revision: 323582

URL: http://llvm.org/viewvc/llvm-project?rev=323582&view=rev
Log:
[GlobalISel][Legalizer] Convert the FP constants to the right APFloat type for G_FCONSTANT.

We weren't converting the immediate ConstantFP during legalization, which caused
the wrong bit patterns to be emitted for half type FP constants.

Fixes PR36106.

Modified:
    llvm/trunk/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
    llvm/trunk/test/CodeGen/AArch64/GlobalISel/legalize-constant.mir

Modified: llvm/trunk/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/GlobalISel/LegalizerHelper.cpp?rev=323582&r1=323581&r2=323582&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/GlobalISel/LegalizerHelper.cpp (original)
+++ llvm/trunk/lib/CodeGen/GlobalISel/LegalizerHelper.cpp Fri Jan 26 23:07:20 2018
@@ -715,7 +715,24 @@ LegalizerHelper::widenScalar(MachineInst
   }
   case TargetOpcode::G_FCONSTANT: {
     unsigned DstExt = MRI.createGenericVirtualRegister(WideTy);
-    MIRBuilder.buildFConstant(DstExt, *MI.getOperand(1).getFPImm());
+    const ConstantFP *CFP = MI.getOperand(1).getFPImm();
+    APFloat Val = CFP->getValueAPF();
+    LLVMContext &Ctx = MIRBuilder.getMF().getFunction().getContext();
+    auto LLT2Sem = [](LLT Ty) {
+      switch (Ty.getSizeInBits()) {
+      case 32:
+        return &APFloat::IEEEsingle();
+        break;
+      case 64:
+        return &APFloat::IEEEdouble();
+        break;
+      default:
+        llvm_unreachable("Unhandled fp widen type");
+      }
+    };
+    bool LosesInfo;
+    Val.convert(*LLT2Sem(WideTy), APFloat::rmTowardZero, &LosesInfo);
+    MIRBuilder.buildFConstant(DstExt, *ConstantFP::get(Ctx, Val));
     MIRBuilder.buildFPTrunc(MI.getOperand(0).getReg(), DstExt);
     MI.eraseFromParent();
     return Legalized;

Modified: llvm/trunk/test/CodeGen/AArch64/GlobalISel/legalize-constant.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/GlobalISel/legalize-constant.mir?rev=323582&r1=323581&r2=323582&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/GlobalISel/legalize-constant.mir (original)
+++ llvm/trunk/test/CodeGen/AArch64/GlobalISel/legalize-constant.mir Fri Jan 26 23:07:20 2018
@@ -75,7 +75,7 @@ body: |
     ; CHECK: %w0 = COPY [[C]](s32)
     ; CHECK: [[C1:%[0-9]+]]:_(s64) = G_FCONSTANT double 2.000000e+00
     ; CHECK: %x0 = COPY [[C1]](s64)
-    ; CHECK: [[C2:%[0-9]+]]:_(s32) = G_FCONSTANT half 0xH0000
+    ; CHECK: [[C2:%[0-9]+]]:_(s32) = G_FCONSTANT float 0.000000e+00
     ; CHECK: [[FPTRUNC:%[0-9]+]]:_(s16) = G_FPTRUNC [[C2]](s32)
     ; CHECK: [[ANYEXT:%[0-9]+]]:_(s32) = G_ANYEXT [[FPTRUNC]](s16)
     ; CHECK: %w0 = COPY [[ANYEXT]](s32)