Revert of MIPS: Add FPXX support to MIPS32R2 (patchset #3 id:40001 of...

Revert of MIPS: Add FPXX support to MIPS32R2 (patchset #3 id:40001 of https://codereview.chromium.org/1586223004/ )

Reason for revert:
Revert patch due to a number of failures appearing on the MIPS v8 simulator

Original issue's description:
> MIPS: Add FPXX support to MIPS32R2
>
> The JIT code generated by V8 is FPXX compliant
> when v8 compiled with FPXX flag. This allows the code to
> run in both FP=1 and FP=0 mode. It also alows v8 to be used
> as a library by both FP32 and FP64 binaries.
>
> BUG=
>
> Committed: https://crrev.com/95110dde666158a230a823fd50a68558ad772320
> Cr-Commit-Position: refs/heads/master@{#33576}

TBR=paul.lind@imgtec.com,gergely.kis@imgtec.com,akos.palfi@imgtec.com,ilija.pavlovic@imgtec.com,marija.antic@imgtec.com,miran.karic@imgtec.com,balazs.kilvady@imgtec.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/1646813003

Cr-Commit-Position: refs/heads/master@{#33583}

src/mips/assembler-mips.cc

@@ -2099,7 +2099,7 @@ void Assembler::ldc1(FPURegister fd, const MemOperand& src) {
       GenInstrImmediate(LW, at, at, Register::kExponentOffset);
       mthc1(at, fd);
     }
-  } else if (IsFp32Mode()) {  // fp32 mode.
+  } else {  // fp32 mode.
     if (is_int16(src.offset_) && is_int16(src.offset_ + kIntSize)) {
       GenInstrImmediate(LWC1, src.rm(), fd,
                         src.offset_ + Register::kMantissaOffset);
@@ -2114,22 +2114,6 @@ void Assembler::ldc1(FPURegister fd, const MemOperand& src) {
       nextfpreg.setcode(fd.code() + 1);
       GenInstrImmediate(LWC1, at, nextfpreg, Register::kExponentOffset);
     }
-  } else {
-    DCHECK(IsFpxxMode());
-    // Currently we support FPXX on Mips32r2 and Mips32r6
-    DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
-    if (is_int16(src.offset_) && is_int16(src.offset_ + kIntSize)) {
-      GenInstrImmediate(LWC1, src.rm(), fd,
-                        src.offset_ + Register::kMantissaOffset);
-      GenInstrImmediate(LW, src.rm(), at,
-                        src.offset_ + Register::kExponentOffset);
-      mthc1(at, fd);
-    } else {  // Offset > 16 bits, use multiple instructions to load.
-      LoadRegPlusOffsetToAt(src);
-      GenInstrImmediate(LWC1, at, fd, Register::kMantissaOffset);
-      GenInstrImmediate(LW, at, at, Register::kExponentOffset);
-      mthc1(at, fd);
-    }
   }
 }
 
@@ -2162,7 +2146,7 @@ void Assembler::sdc1(FPURegister fd, const MemOperand& src) {
       mfhc1(t8, fd);
       GenInstrImmediate(SW, at, t8, Register::kExponentOffset);
     }
-  } else if (IsFp32Mode()) {  // fp32 mode.
+  } else {  // fp32 mode.
     if (is_int16(src.offset_) && is_int16(src.offset_ + kIntSize)) {
       GenInstrImmediate(SWC1, src.rm(), fd,
                         src.offset_ + Register::kMantissaOffset);
@@ -2177,22 +2161,6 @@ void Assembler::sdc1(FPURegister fd, const MemOperand& src) {
       nextfpreg.setcode(fd.code() + 1);
       GenInstrImmediate(SWC1, at, nextfpreg, Register::kExponentOffset);
     }
-  } else {
-    DCHECK(IsFpxxMode());
-    // Currently we support FPXX on Mips32r2 and Mips32r6
-    DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
-    if (is_int16(src.offset_) && is_int16(src.offset_ + kIntSize)) {
-      GenInstrImmediate(SWC1, src.rm(), fd,
-                        src.offset_ + Register::kMantissaOffset);
-      mfhc1(at, fd);
-      GenInstrImmediate(SW, src.rm(), at,
-                        src.offset_ + Register::kExponentOffset);
-    } else {  // Offset > 16 bits, use multiple instructions to load.
-      LoadRegPlusOffsetToAt(src);
-      GenInstrImmediate(SWC1, at, fd, Register::kMantissaOffset);
-      mfhc1(t8, fd);
-      GenInstrImmediate(SW, at, t8, Register::kExponentOffset);
-    }
   }
 }
 

src/mips/constants-mips.h

@@ -64,13 +64,9 @@ enum FpuMode {
 #elif defined(FPU_MODE_FP64)
   static const FpuMode kFpuMode = kFP64;
 #elif defined(FPU_MODE_FPXX)
-#if defined(_MIPS_ARCH_MIPS32R2) || defined(_MIPS_ARCH_MIPS32R6)
-static const FpuMode kFpuMode = kFPXX;
+  static const FpuMode kFpuMode = kFPXX;
 #else
-#error "FPXX is supported only on Mips32R2 and Mips32R6"
-#endif
-#else
-static const FpuMode kFpuMode = kFP32;
+  static const FpuMode kFpuMode = kFP32;
 #endif
 
 #if(defined(__mips_hard_float) && __mips_hard_float != 0)
@@ -96,9 +92,13 @@ const uint32_t kHoleNanLower32Offset = 4;
 #error Unknown endianness
 #endif
 
-#define IsFp64Mode() (kFpuMode == kFP64)
-#define IsFp32Mode() (kFpuMode == kFP32)
-#define IsFpxxMode() (kFpuMode == kFPXX)
+#ifndef FPU_MODE_FPXX
+#define IsFp64Mode() \
+  (kFpuMode == kFP64)
+#else
+#define IsFp64Mode() \
+  (CpuFeatures::IsSupported(FP64FPU))
+#endif
 
 #ifndef _MIPS_ARCH_MIPS32RX
 #define IsMipsArchVariant(check) \

src/mips/macro-assembler-mips.cc

@@ -1396,7 +1396,7 @@ void MacroAssembler::Trunc_uw_d(FPURegister fd,
 
 
 void MacroAssembler::Mthc1(Register rt, FPURegister fs) {
-  if (IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6)) {
+  if (IsFp64Mode()) {
     mthc1(rt, fs);
   } else {
     mtc1(rt, fs.high());
@@ -1405,7 +1405,7 @@ void MacroAssembler::Mthc1(Register rt, FPURegister fs) {
 
 
 void MacroAssembler::Mfhc1(Register rt, FPURegister fs) {
-  if (IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6)) {
+  if (IsFp64Mode()) {
     mfhc1(rt, fs);
   } else {
     mfc1(rt, fs.high());

test/cctest/test-assembler-mips.cc

@@ -384,14 +384,6 @@ TEST(MIPS3) {
 
 
 TEST(MIPS4) {
-  // Exchange between GP anf FP registers is done through memory
-  // on FPXX compiled binaries and architectures that do not support
-  // MTHC1 and MTFC1. If this is the case, skipping this test.
-  if (IsFpxxMode() &&
-      (IsMipsArchVariant(kMips32r1) || IsMipsArchVariant(kLoongson))) {
-    return;
-  }
-
   // Test moves between floating point and integer registers.
   CcTest::InitializeVM();
   Isolate* isolate = CcTest::i_isolate();
@@ -411,7 +403,7 @@ TEST(MIPS4) {
   __ ldc1(f6, MemOperand(a0, offsetof(T, b)) );
 
   // Swap f4 and f6, by using four integer registers, t0-t3.
-  if (IsFp32Mode()) {
+  if (!IsFp64Mode()) {
     __ mfc1(t0, f4);
     __ mfc1(t1, f5);
     __ mfc1(t2, f6);
@@ -423,7 +415,6 @@ TEST(MIPS4) {
     __ mtc1(t3, f5);
   } else {
     CHECK(!IsMipsArchVariant(kMips32r1) && !IsMipsArchVariant(kLoongson));
-    DCHECK(IsFp64Mode() || IsFpxxMode());
     __ mfc1(t0, f4);
     __ mfhc1(t1, f4);
     __ mfc1(t2, f6);
@@ -434,7 +425,6 @@ TEST(MIPS4) {
     __ mtc1(t2, f4);
     __ mthc1(t3, f4);
   }
-
   // Store the swapped f4 and f5 back to memory.
   __ sdc1(f4, MemOperand(a0, offsetof(T, a)) );
   __ sdc1(f6, MemOperand(a0, offsetof(T, c)) );
@@ -821,6 +811,8 @@ TEST(MIPS9) {
 
 TEST(MIPS10) {
   // Test conversions between doubles and words.
+  // Test maps double to FP reg pairs in fp32 mode
+  // and into FP reg in fp64 mode.
   CcTest::InitializeVM();
   Isolate* isolate = CcTest::i_isolate();
   HandleScope scope(isolate);
@@ -838,16 +830,24 @@ TEST(MIPS10) {
   Assembler assm(isolate, NULL, 0);
   Label L, C;
 
-  if (IsMipsArchVariant(kMips32r1) || IsMipsArchVariant(kLoongson)) return;
+  if (!IsMipsArchVariant(kMips32r2)) return;
 
   // Load all structure elements to registers.
   // (f0, f1) = a (fp32), f0 = a (fp64)
   __ ldc1(f0, MemOperand(a0, offsetof(T, a)));
 
-  __ mfc1(t0, f0);   // t0 = f0(31..0)
-  __ mfhc1(t1, f0);  // t1 = sign_extend(f0(63..32))
-  __ sw(t0, MemOperand(a0, offsetof(T, dbl_mant)));  // dbl_mant = t0
-  __ sw(t1, MemOperand(a0, offsetof(T, dbl_exp)));   // dbl_exp = t1
+  if (IsFp64Mode()) {
+    __ mfc1(t0, f0);  // t0 = f0(31..0)
+    __ mfhc1(t1, f0);  // t1 = sign_extend(f0(63..32))
+    __ sw(t0, MemOperand(a0, offsetof(T, dbl_mant)));  // dbl_mant = t0
+    __ sw(t1, MemOperand(a0, offsetof(T, dbl_exp)));  // dbl_exp = t1
+  } else {
+    // Save the raw bits of the double.
+    __ mfc1(t0, f0);  // t0 = a1
+    __ mfc1(t1, f1);  // t1 = a2
+    __ sw(t0, MemOperand(a0, offsetof(T, dbl_mant)));  // dbl_mant = t0
+    __ sw(t1, MemOperand(a0, offsetof(T, dbl_exp)));  // dbl_exp = t1
+  }
 
   // Convert double in f0 to word, save hi/lo parts.
   __ cvt_w_d(f0, f0);  // a_word = (word)a