[wasm] Implementation of Word32PairShr and Word32PairSar on arm.

src/arm/macro-assembler-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
@@ skipping 1127 matching lines @@
   } else if (shift == 0) {
     Move(dst_high, src_high);
     Move(dst_low, src_low);
   } else {
     lsl(dst_high, src_high, Operand(shift));
     orr(dst_high, dst_high, Operand(src_low, LSR, 32 - shift));
     lsl(dst_low, src_low, Operand(shift));
   }
 }
 
+void MacroAssembler::LsrPair(Register dst_low, Register dst_high,
+                             Register src_low, Register src_high,
+                             Register scratch, Register shift) {
+  DCHECK(!AreAliased(dst_low, src_high));
+  DCHECK(!AreAliased(dst_low, shift));
+
+  Label less_than_32;
+  Label done;
+  cmp_raw_immediate(shift, 32);

[Rodolph Perfetta (ARM), 2016/03/10 14:48:10]

If you move the rsb up here you can use it to do the compare:

  rsb(scratch, shift, Operand(32), SetCC);
  b(gt, &less_than_32);
  ...

[ahaas, 2016/03/10 15:33:35]

Thanks, I do the same now for LslPair. If I use SetCC, should I also add the
"DCHECK_EQ(LeaveCC, i.OutputSBit());"? Could you explain me what this DCHECK
actually checks?

[ahaas, 2016/03/10 18:00:52]

Done.

+  b(lt, &less_than_32);
+  // If shift >= 32
+  and_(scratch, shift, Operand(0x1f));
+  lsr(dst_low, src_high, Operand(scratch));
+  mov(dst_high, Operand(0));
+  jmp(&done);
+  bind(&less_than_32);
+  // If shift < 32
+  rsb(scratch, shift, Operand(32));
+  lsr(dst_low, src_low, Operand(shift));
+  orr(dst_low, dst_low, Operand(src_high, LSL, scratch));
+  lsr(dst_high, src_high, Operand(shift));
+  bind(&done);
+}
+
+void MacroAssembler::LsrPair(Register dst_low, Register dst_high,
+                             Register src_low, Register src_high,
+                             uint32_t shift) {
+  DCHECK(!AreAliased(dst_low, src_high));
+  Label less_than_32;
+  Label done;
+  if (shift == 32) {
+    mov(dst_low, src_high);
+    mov(dst_high, Operand(0));
+  } else if (shift > 32) {
+    shift &= 0x1f;
+    lsr(dst_low, src_high, Operand(shift));
+    mov(dst_high, Operand(0));
+  } else if (shift == 0) {
+    Move(dst_low, src_low);
+    Move(dst_high, src_high);
+  } else {
+    lsr(dst_low, src_low, Operand(shift));
+    orr(dst_low, dst_low, Operand(src_high, LSL, 32 - shift));
+    lsr(dst_high, src_high, Operand(shift));
+  }
+}
+
+void MacroAssembler::AsrPair(Register dst_low, Register dst_high,
+                             Register src_low, Register src_high,
+                             Register scratch, Register shift) {
+  DCHECK(!AreAliased(dst_low, src_high));
+  DCHECK(!AreAliased(dst_low, shift));
+
+  Label less_than_32;
+  Label done;
+  cmp_raw_immediate(shift, 32);
+  b(lt, &less_than_32);
+  // If shift >= 32
+  and_(scratch, shift, Operand(0x1f));
+  asr(dst_low, src_high, Operand(scratch));
+  asr(dst_high, src_high, Operand(31));
+  jmp(&done);
+  bind(&less_than_32);
+  // If shift < 32
+  rsb(scratch, shift, Operand(32));
+  lsr(dst_low, src_low, Operand(shift));
+  orr(dst_low, dst_low, Operand(src_high, LSL, scratch));
+  asr(dst_high, src_high, Operand(shift));
+  bind(&done);
+}
+
+void MacroAssembler::AsrPair(Register dst_low, Register dst_high,
+                             Register src_low, Register src_high,
+                             uint32_t shift) {
+  DCHECK(!AreAliased(dst_low, src_high));
+  Label less_than_32;
+  Label done;
+  if (shift == 32) {
+    mov(dst_low, src_high);
+    asr(dst_high, src_high, Operand(31));
+  } else if (shift > 32) {
+    shift &= 0x1f;
+    asr(dst_low, src_high, Operand(shift));
+    asr(dst_high, src_high, Operand(31));
+  } else if (shift == 0) {
+    Move(dst_low, src_low);
+    Move(dst_high, src_high);
+  } else {
+    lsr(dst_low, src_low, Operand(shift));
+    orr(dst_low, dst_low, Operand(src_high, LSL, 32 - shift));
+    asr(dst_high, src_high, Operand(shift));
+  }
+}
+
 void MacroAssembler::LoadConstantPoolPointerRegisterFromCodeTargetAddress(
     Register code_target_address) {
   DCHECK(FLAG_enable_embedded_constant_pool);
   ldr(pp, MemOperand(code_target_address,
                      Code::kConstantPoolOffset - Code::kHeaderSize));
   add(pp, pp, code_target_address);
 }
 
 
 void MacroAssembler::LoadConstantPoolPointerRegister() {
@@ skipping 2678 matching lines @@
     }
   }
   if (mag.shift > 0) mov(result, Operand(result, ASR, mag.shift));
   add(result, result, Operand(dividend, LSR, 31));
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM