[ARM] Disabling vfp4 should disable fp16

[john.brawn]

Summary

ARMTargetParser::getFPUFeatures should disable fp16 whenever it disables vfp4, as otherwise something like -mcpu=cortex-a7 -mfpu=none leaves us with fp16 enabled (though the only effect that will have is a wrong build attribute).

[rengolin]

LGTM

lib/Support/TargetParser.cpp

bool ARMTargetParser::getFPUFeatures(unsigned FPUKind,
   case ARM::FR_None:
     Features.push_back("-fp-only-sp");
     Features.push_back("-d16");
     break;
   }
 
   // FPU version subtarget features are inclusive of lower-numbered ones, so
   // enable the one corresponding to this version and disable all that are
-  // higher.
+  // higher. We also have to make sure to disable fp16 when vfp4 is disabled,
+  // as +vfp4 implies +fp16 but -vfp4 does not imply -fp16.
   switch (FPUNames[FPUKind].FPUVersion) {
   case 5:
     Features.push_back("+fp-armv8");
     break;
   case 4:
     Features.push_back("+vfp4");
     Features.push_back("-fp-armv8");
     break;
   case 3:
     Features.push_back("+vfp3");
+    Features.push_back("-fp16");
     Features.push_back("-vfp4");
     Features.push_back("-fp-armv8");
     break;
   case 2:
     Features.push_back("+vfp2");
     Features.push_back("-vfp3");
+    Features.push_back("-fp16");
     Features.push_back("-vfp4");
     Features.push_back("-fp-armv8");
     break;
   case 0:
     Features.push_back("-vfp2");
     Features.push_back("-vfp3");
+    Features.push_back("-fp16");
     Features.push_back("-vfp4");
     Features.push_back("-fp-armv8");
     break;
   }
 
   // crypto includes neon, so we handle this similarly to FPU version.
   switch (FPUNames[FPUKind].NeonSupport) {
   case ARM::NS_Crypto:

test/CodeGen/ARM/build-attributes.ll

 ; RUN: llc < %s -mtriple=armv8-linux-gnueabi -mcpu=cortex-a72 | FileCheck %s --check-prefix=CORTEX-A72
 ; RUN: llc < %s -mtriple=armv8-linux-gnueabi -mcpu=cortex-a72  -enable-unsafe-fp-math -disable-fp-elim -enable-no-infs-fp-math -enable-no-nans-fp-math -fp-contract=fast | FileCheck %s --check-prefix=CORTEX-A72-FAST
 ; RUN: llc < %s -mtriple=armv8-linux-gnueabi -mcpu=cortex-a72 -enable-sign-dependent-rounding-fp-math | FileCheck %s --check-prefix=DYN-ROUNDING
 ; RUN: llc < %s -mtriple=armv8.1a-linux-gnueabi | FileCheck %s --check-prefix=GENERIC-ARMV8_1-A
 ; RUN: llc < %s -mtriple=armv8.1a-linux-gnueabi  -enable-unsafe-fp-math -disable-fp-elim -enable-no-infs-fp-math -enable-no-nans-fp-math -fp-contract=fast | FileCheck %s --check-prefix=GENERIC-ARMV8_1-A-FAST
 ; RUN: llc < %s -mtriple=armv8.1a-linux-gnueabi -enable-sign-dependent-rounding-fp-math | FileCheck %s --check-prefix=DYN-ROUNDING
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 | FileCheck %s  --check-prefix=CORTEX-A7-CHECK
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7  -enable-unsafe-fp-math -disable-fp-elim -enable-no-infs-fp-math -enable-no-nans-fp-math -fp-contract=fast | FileCheck %s  --check-prefix=CORTEX-A7-CHECK-FAST
-; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=-vfp2,-vfp3,-vfp4,-neon | FileCheck %s --check-prefix=CORTEX-A7-NOFPU
-; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=-vfp2,-vfp3,-vfp4,-neon  -enable-unsafe-fp-math -disable-fp-elim -enable-no-infs-fp-math -enable-no-nans-fp-math -fp-contract=fast | FileCheck %s --check-prefix=CORTEX-A7-NOFPU-FAST
+; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=-vfp2,-vfp3,-vfp4,-neon,-fp16 | FileCheck %s --check-prefix=CORTEX-A7-NOFPU
+; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=-vfp2,-vfp3,-vfp4,-neon,-fp16  -enable-unsafe-fp-math -disable-fp-elim -enable-no-infs-fp-math -enable-no-nans-fp-math -fp-contract=fast | FileCheck %s --check-prefix=CORTEX-A7-NOFPU-FAST
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=+vfp4,-neon | FileCheck %s --check-prefix=CORTEX-A7-FPUV4
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -enable-sign-dependent-rounding-fp-math | FileCheck %s --check-prefix=DYN-ROUNDING
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=+vfp4,-neon  -enable-unsafe-fp-math -disable-fp-elim -enable-no-infs-fp-math -enable-no-nans-fp-math -fp-contract=fast | FileCheck %s --check-prefix=CORTEX-A7-FPUV4-FAST
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=+vfp4,,+d16,-neon | FileCheck %s --check-prefix=CORTEX-A7-FPUV4
 ; RUN: llc < %s -mtriple=arm-none-linux-gnueabi -relocation-model=pic | FileCheck %s --check-prefix=RELOC-PIC
 ; RUN: llc < %s -mtriple=arm-none-linux-gnueabi -relocation-model=static | FileCheck %s --check-prefix=RELOC-OTHER
 ; RUN: llc < %s -mtriple=arm-none-linux-gnueabi -relocation-model=default | FileCheck %s --check-prefix=RELOC-OTHER
 ; RUN: llc < %s -mtriple=arm-none-linux-gnueabi -relocation-model=dynamic-no-pic | FileCheck %s --check-prefix=RELOC-OTHER

 
 ; Tag_ABI_align_preserved
 ; CORTEX-A7-CHECK: .eabi_attribute      25, 1
 ; CORTEX-A7-NOFPU: .eabi_attribute      25, 1
 ; CORTEX-A7-FPUV4: .eabi_attribute      25, 1
 
 ; Tag_FP_HP_extension
 ; CORTEX-A7-CHECK: .eabi_attribute      36, 1
-; CORTEX-A7-NOFPU: .eabi_attribute      36, 1
+; CORTEX-A7-NOFPU-NOT: .eabi_attribute  36
 ; CORTEX-A7-FPUV4: .eabi_attribute      36, 1
 
 ; Tag_FP_16bit_format
 ; CORTEX-A7-CHECK: .eabi_attribute      38, 1
 ; CORTEX-A7-NOFPU: .eabi_attribute      38, 1
 ; CORTEX-A7-FPUV4: .eabi_attribute      38, 1
 
 ; Tag_MPextension_use