ARM: Use the shifter operand to merge in previous shift instructions.

ARM: Use the shifter operand to merge in previous shift instructions.

When possible, we transform sequences of code of the form
    lsl r1, r2, #imm
    add r0, r5, r1
into
    add r0, r5, r2 LSL #imm

This is an adaptation of r21161.

R=ulan@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=22017

[Alexandre Rames, 2014-06-04 15:03:40]

This is a port of the arm64 similar commit.

[ulan, 2014-06-10 11:53:37]

LGTM with comments:

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-arm.cc
File src/arm/lithium-arm.cc (right):

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-arm.cc#newco...
src/arm/lithium-arm.cc:809: constant_value = constant->Integer32Value() & 0x1f;
Use JSShiftAmountFromHConstant?

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-codegen-arm.cc
File src/arm/lithium-codegen-arm.cc (right):

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-codegen-arm....
src/arm/lithium-codegen-arm.cc:1731: right = ToOperand(right_op);
Doesn't ToShiftedRightOperand take care of this case?

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-codegen-arm....
src/arm/lithium-codegen-arm.cc:1793: uint8_t shift_count =
static_cast<uint8_t>(value & 0x1F);
The original CL used JSShiftAmountFromLConstant here and in other places.

[Alexandre Rames, 2014-06-11 10:19:40]

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-arm.cc
File src/arm/lithium-arm.cc (right):

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-arm.cc#newco...
src/arm/lithium-arm.cc:809: constant_value = constant->Integer32Value() & 0x1f;
On 2014/06/10 11:53:37, ulan wrote:
> Use JSShiftAmountFromHConstant?

Done.

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-codegen-arm.cc
File src/arm/lithium-codegen-arm.cc (right):

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-codegen-arm....
src/arm/lithium-codegen-arm.cc:1731: right = ToOperand(right_op);
On 2014/06/10 11:53:37, ulan wrote:
> Doesn't ToShiftedRightOperand take care of this case?

It does. Removed the constant case.

https://codereview.chromium.org/312173002/diff/1/src/arm/lithium-codegen-arm....
src/arm/lithium-codegen-arm.cc:1793: uint8_t shift_count =
static_cast<uint8_t>(value & 0x1F);
On 2014/06/10 11:53:37, ulan wrote:
> The original CL used JSShiftAmountFromLConstant here and in other places.

Done.

[Alexandre Rames, 2014-06-11 10:20:47]

Uploaded the patch with your comments addressed. Could you confirm it is still
ok to go in? Thanks

[Alexandre Rames, 2014-06-25 15:11:23]

Committed patchset #2 manually as r22017 (presubmit successful).