[arm][turbofan] Remove hard-coded uses of r9 and allocate it.

Remove hard-coded scratch registers (r9 and ip) from the code generator in favor
of using the `UseScratchRegisterScope` utility. And as a result, we can free the
r9 register for the allocator to use.

Note that the code generator now has to cope with a single scratch register (ip)
instead of two (ip + r9). Therefore the code sequences emitted by moves aren't
as optimized as they used to be. For instance, we now use a scratch S register
in places where we could use r9. We can optimize them further if we want but
running benchmarks showed no impact so keeping the code simpler was deemed
better for the time being.

Bug: v8:6553
Change-Id: I7fcf244cb1b6578564b503619a041006eaf74626
Reviewed-on: https://chromium-review.googlesource.com/895461
Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51080}

src/arm/assembler-arm.h

@@ -56,8 +56,9 @@ namespace internal {
   V(r0)  V(r1)  V(r2)  V(r3)  V(r4)  V(r5)  V(r6)  V(r7)  \
   V(r8)  V(r9)  V(r10) V(fp)  V(ip)  V(sp)  V(lr)  V(pc)
 
-#define ALLOCATABLE_GENERAL_REGISTERS(V) \
-  V(r0)  V(r1)  V(r2)  V(r3)  V(r4)  V(r5)  V(r6)  V(r7)  V(r8)
+#define ALLOCATABLE_GENERAL_REGISTERS(V)                  \
+  V(r0)  V(r1)  V(r2)  V(r3)  V(r4)  V(r5)  V(r6)  V(r7)  \
+  V(r8)  V(r9)
 
 #define FLOAT_REGISTERS(V)                                \
   V(s0)  V(s1)  V(s2)  V(s3)  V(s4)  V(s5)  V(s6)  V(s7)  \

src/arm/macro-assembler-arm.cc

@@ -940,9 +940,11 @@ void TurboAssembler::ReplaceLane(QwNeonRegister dst, QwNeonRegister src,
 
 void TurboAssembler::LslPair(Register dst_low, Register dst_high,
                              Register src_low, Register src_high,
-                             Register scratch, Register shift) {
+                             Register shift) {
   DCHECK(!AreAliased(dst_high, src_low));
   DCHECK(!AreAliased(dst_high, shift));
+  UseScratchRegisterScope temps(this);
+  Register scratch = temps.Acquire();
 
   Label less_than_32;
   Label done;
@@ -986,9 +988,11 @@ void TurboAssembler::LslPair(Register dst_low, Register dst_high,
 
 void TurboAssembler::LsrPair(Register dst_low, Register dst_high,
                              Register src_low, Register src_high,
-                             Register scratch, Register shift) {
+                             Register shift) {
   DCHECK(!AreAliased(dst_low, src_high));
   DCHECK(!AreAliased(dst_low, shift));
+  UseScratchRegisterScope temps(this);
+  Register scratch = temps.Acquire();
 
   Label less_than_32;
   Label done;
@@ -1033,9 +1037,11 @@ void TurboAssembler::LsrPair(Register dst_low, Register dst_high,
 
 void TurboAssembler::AsrPair(Register dst_low, Register dst_high,
                              Register src_low, Register src_high,
-                             Register scratch, Register shift) {
+                             Register shift) {
   DCHECK(!AreAliased(dst_low, src_high));
   DCHECK(!AreAliased(dst_low, shift));
+  UseScratchRegisterScope temps(this);
+  Register scratch = temps.Acquire();
 
   Label less_than_32;
   Label done;

src/arm/macro-assembler-arm.h

@@ -308,15 +308,15 @@ class TurboAssembler : public Assembler {
   inline bool AllowThisStubCall(CodeStub* stub);
 
   void LslPair(Register dst_low, Register dst_high, Register src_low,
-               Register src_high, Register scratch, Register shift);
+               Register src_high, Register shift);
   void LslPair(Register dst_low, Register dst_high, Register src_low,
                Register src_high, uint32_t shift);
   void LsrPair(Register dst_low, Register dst_high, Register src_low,
-               Register src_high, Register scratch, Register shift);
+               Register src_high, Register shift);
   void LsrPair(Register dst_low, Register dst_high, Register src_low,
                Register src_high, uint32_t shift);
   void AsrPair(Register dst_low, Register dst_high, Register src_low,
-               Register src_high, Register scratch, Register shift);
+               Register src_high, Register shift);
   void AsrPair(Register dst_low, Register dst_high, Register src_low,
                Register src_high, uint32_t shift);