[RISCV] Don't parse the decimal minimum value for fli.s/fli.d/fli.h.

[craig.topper]

Summary

There are a couple bugs in the current support for this:
-We do all the parsing in single precision so any value less than or
equal to the minimum fp32 is accepted as the minimum value for f64.
-To support fp16 minimum value, getLoadFP32Imm has a special case, but
that causes a miscompile in CodeGen.

[asb]

LGTM.

[joshua-arch1]

@craig.topper Since we parse the instructions using double precision and use separate lookup tables for fli.h/fli.d now, I think there are no reason not to parse minimum values for FLI.

[craig.topper]

In D145542#4195310, @joshua-arch1 wrote:

@craig.topper Since we parse the instructions using double precision and use separate lookup tables for fli.h/fli.d now, I think there are no reason not to parse minimum v

In D145542#4195310, @joshua-arch1 wrote:

@craig.topper Since we parse the instructions using double precision and use separate lookup tables for fli.h/fli.d now, I think there are no reason not to parse minimum values for FLI.

The min value for double is very long. I don’t think anyone would use it. I think we should ask on the riscv-isa-manual GitHub before supporting it.

[joshua-arch1]

In D145542#4195327, @craig.topper wrote:

In D145542#4195310, @joshua-arch1 wrote:

@craig.topper Since we parse the instructions using double precision and use separate lookup tables for fli.h/fli.d now, I think there are no reason not to parse minimum v

In D145542#4195310, @joshua-arch1 wrote:

@craig.topper Since we parse the instructions using double precision and use separate lookup tables for fli.h/fli.d now, I think there are no reason not to parse minimum values for FLI.

The min value for double is very long. I don’t think anyone would use it. I think we should ask on the riscv-isa-manual GitHub before supporting it.

I think we can at least test min value for half. Also, the min value for double is 2^(-1022) which is a certain number. There will be some circumstances where someone will use its specific value.

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

 //===-- RISCVAsmParser.cpp - Parse RISCV assembly to MCInst instructions --===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
public:
   /// Return true if the operand is a valid floating point rounding mode.
   bool isFRMArg() const { return Kind == KindTy::FRM; }
   bool isRTZArg() const { return isFRMArg() && FRM.FRM == RISCVFPRndMode::RTZ; }
 
   /// Return true if the operand is a valid fli.s floating-point immediate.
   bool isLoadFPImm() const {
     if (isImm())
       return isUImm5();
-    return Kind == KindTy::FPImmediate &&
-           RISCVLoadFPImm::getLoadFP32Imm(APInt(32, getFPConst())) != -1;
+    if (Kind != KindTy::FPImmediate)
+      return false;
+    int Idx = RISCVLoadFPImm::getLoadFP32Imm(APInt(32, getFPConst()));
+    // Don't allow decimal version of the minimum value. It is a different value
+    // for each supported data type.
+    return Idx >= 0 && Idx != 1;
   }
 
   bool isImmXLenLI() const {
     int64_t Imm;
     RISCVMCExpr::VariantKind VK = RISCVMCExpr::VK_RISCV_None;
     if (!isImm())
       return false;
     bool IsConstantImm = evaluateConstantImm(getImm(), Imm, VK);

llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h

 //===-- RISCVBaseInfo.h - Top level definitions for RISCV MC ----*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
inline static uint32_t getFPImm(unsigned Imm) {
 
   return Sign << 31 | Exp << 23 | Mantissa << 20;
 }
 
 /// getLoadFP32Imm - Return a 5-bit binary encoding of the 32-bit
 /// floating-point immediate value. If the value cannot be represented as a
 /// 5-bit binary encoding, then return -1.
 static inline int getLoadFP32Imm(const APInt &Imm) {
-  if ((Imm.extractBitsAsZExtValue(9, 23) == 0b001110001 &&
-       Imm.extractBitsAsZExtValue(23, 0) == 0) ||
-       Imm.extractBitsAsZExtValue(32, 0) == 0)
-    return 1;
-
   if (Imm.extractBitsAsZExtValue(20, 0) != 0)
     return -1;
 
   uint8_t Sign = Imm.extractBitsAsZExtValue(1, 31);
   uint8_t Exp = Imm.extractBitsAsZExtValue(8, 23);
   uint8_t Mantissa = Imm.extractBitsAsZExtValue(3, 20);
   return getLoadFPImm(Sign, Exp, Mantissa);
 }

llvm/test/CodeGen/RISCV/float-zfa.ll

 ; CHECK-LABEL: loadfpimm9:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    lui a0, 276464
 ; CHECK-NEXT:    fmv.w.x fa0, a0
 ; CHECK-NEXT:    ret
   ret float 255.0
 }
 
-; FIXME: This is the f16 minimum value. It should not be supported for f32.
+; This is the f16 minimum value. Make sure we don't use fli.s.
 define float @loadfpimm10() {
 ; CHECK-LABEL: loadfpimm10:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    fli.s fa0, min
+; CHECK-NEXT:    lui a0, 231424
+; CHECK-NEXT:    fmv.w.x fa0, a0
 ; CHECK-NEXT:    ret
   ret float 0.00006103515625
 }
 
 declare float @llvm.minimum.f32(float, float)
 
 define float @fminm_s(float %a, float %b) nounwind {
 ; CHECK-LABEL: fminm_s:

llvm/test/MC/RISCV/zfa-invalid.s

 
 # CHECK-NO-RV64: error: invalid floating point immediate
 # CHECK-NO-RV32: error: invalid floating point immediate
 fli.s ft1, -inf
 
 # CHECK-NO-RV64: error: invalid floating point immediate
 # CHECK-NO-RV32: error: invalid floating point immediate
 fli.s ft1, -nan
+
+# Don't accept decimal minimum.
+# CHECK-NO-RV64: error: operand must be a valid floating-point constant
+# CHECK-NO-RV32: error: operand must be a valid floating-point constant
+fli.s ft1, 1.1754943508222875079687365372222456778186655567720875215087517062784172594547271728515625e-38
+
+# Don't accept decimal minimum.
+# CHECK-NO-RV64: error: operand must be a valid floating-point constant
+# CHECK-NO-RV32: error: operand must be a valid floating-point constant
+fli.d ft1, 2.225073858507201383090232717332404064219215980462331830553327416887204434813918195854283159012511020564067339731035811005152434161553460108856012385377718821130777993532002330479610147442583636071921565046942503734208375250806650616658158948720491179968591639648500635908770118304874799780887753749949451580451605050915399856582470818645113537935804992115981085766051992433352114352390148795699609591288891602992641511063466313393663477586513029371762047325631781485664350872122828637642044846811407613911477062801689853244110024161447421618567166150540154285084716752901903161322778896729707373123334086988983175067838846926092773977972858659654941091369095406136467568702398678315290680984617210924625396728515625e-308
+
+# Don't accept decimal minimum.
+# CHECK-NO-RV64: error: operand must be a valid floating-point constant
+# CHECK-NO-RV32: error: operand must be a valid floating-point constant
+fli.h ft1, 6.103516e-05
+
+# Don't accept single precision minimum for double.
+# CHECK-NO-RV64: error: operand must be a valid floating-point constant
+# CHECK-NO-RV32: error: operand must be a valid floating-point constant
+fli.d ft1, 1.1754943508222875079687365372222456778186655567720875215087517062784172594547271728515625e-38
+
+# Don't accept single precision minimum for half.
+# CHECK-NO-RV64: error: operand must be a valid floating-point constant
+# CHECK-NO-RV32: error: operand must be a valid floating-point constant
+fli.h ft1, 1.1754943508222875079687365372222456778186655567720875215087517062784172594547271728515625e-38
+

llvm/test/MC/RISCV/zfa-valid.s

 # CHECK-ASM-AND-OBJ: fli.s ft1, -1.000000e+00
 # CHECK-ASM: encoding: [0xd3,0x00,0x10,0xf0]
 # CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
 fli.s ft1, -1.000000e+00
 
 # CHECK-ASM-AND-OBJ: fli.s ft1, min
 # CHECK-ASM: encoding: [0xd3,0x80,0x10,0xf0]
 # CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
-fli.s ft1, 1.1754943508222875079687365372222456778186655567720875215087517062784172594547271728515625e-38
-
-# CHECK-ASM-AND-OBJ: fli.s ft1, min
-# CHECK-ASM: encoding: [0xd3,0x80,0x10,0xf0]
-# CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
 fli.s ft1, min
 
 # CHECK-ASM-AND-OBJ: fli.s ft1, 1.525879e-05
 # CHECK-ASM: encoding: [0xd3,0x00,0x11,0xf0]
 # CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
 fli.s ft1, 1.525879e-05
 
 # CHECK-ASM-AND-OBJ: fli.s ft1, 3.051758e-05

 # CHECK-ASM-AND-OBJ: fli.d ft1, -1.000000e+00
 # CHECK-ASM: encoding: [0xd3,0x00,0x10,0xf2]
 # CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
 fli.d ft1, -1.000000e+00
 
 # CHECK-ASM-AND-OBJ: fli.d ft1, min
 # CHECK-ASM: encoding: [0xd3,0x80,0x10,0xf2]
 # CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
-fli.d ft1, 2.225073858507201383090232717332404064219215980462331830553327416887204434813918195854283159012511020564067339731035811005152434161553460108856012385377718821130777993532002330479610147442583636071921565046942503734208375250806650616658158948720491179968591639648500635908770118304874799780887753749949451580451605050915399856582470818645113537935804992115981085766051992433352114352390148795699609591288891602992641511063466313393663477586513029371762047325631781485664350872122828637642044846811407613911477062801689853244110024161447421618567166150540154285084716752901903161322778896729707373123334086988983175067838846926092773977972858659654941091369095406136467568702398678315290680984617210924625396728515625e-308
-
-# CHECK-ASM-AND-OBJ: fli.d ft1, min
-# CHECK-ASM: encoding: [0xd3,0x80,0x10,0xf2]
-# CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
 fli.d ft1, min
 
 # CHECK-ASM-AND-OBJ: fli.d ft1, 1.525879e-05
 # CHECK-ASM: encoding: [0xd3,0x00,0x11,0xf2]
 # CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
 fli.d ft1, 1.525879e-05
 
 # CHECK-ASM-AND-OBJ: fli.d ft1, 3.051758e-05

 # CHECK-ASM-AND-OBJ: fli.h ft1, -1.000000e+00
 # CHECK-ASM: encoding: [0xd3,0x00,0x10,0xf4]
 # CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
 fli.h ft1, -1.000000e+00
 
 # CHECK-ASM-AND-OBJ: fli.h ft1, min
 # CHECK-ASM: encoding: [0xd3,0x80,0x10,0xf4]
 # CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
-fli.h ft1, 6.103516e-05
-
-# CHECK-ASM-AND-OBJ: fli.h ft1, min
-# CHECK-ASM: encoding: [0xd3,0x80,0x10,0xf4]
-# CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
 fli.h ft1, min
 
 # CHECK-ASM-AND-OBJ: fli.h ft1, 1.525879e-05
 # CHECK-ASM: encoding: [0xd3,0x00,0x11,0xf4]
 # CHECK-NO-EXT: error: instruction requires the following: 'Zfa' (Additional Floating-Point){{$}}
 fli.h ft1, 1.525879e-05
 
 # CHECK-ASM-AND-OBJ: fli.h ft1, 3.051758e-05