commit ba56d060116d6e145be348fa575314654c6b0572
author Mark Mendell <mark.p.mendell@intel.com> Tue May 05 21:34:03 2015 -0400
committer Mark Mendell <mark.p.mendell@intel.com> Mon May 11 08:44:54 2015 -0400
tree 4ef90809f6628435a60320b8fa0fd939849e2d29
parent 6727a48193db2a0cf01af971cccffe1a6518c247

[optimizing] Improve 32 bit long shift by 1.

Also change FOO << 1 to FOO+FOO in the instruction simplifier.  This is
an architecture independent simplification, which helps 'long << 1' for
32 bit architectures.

Generate an add/adc for long << 1 in x86, in case something is generated
after the simplifier.

Add test cases for the simplification.

Change-Id: I0d512331ef13cc4ccf10c80f11c370a10ed02294
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>

compiler/optimizing/code_generator_x86.cc

diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index cfb8702..2848a48 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -2830,7 +2830,11 @@
 void InstructionCodeGeneratorX86::GenerateShlLong(const Location& loc, int shift) {
   Register low = loc.AsRegisterPairLow<Register>();
   Register high = loc.AsRegisterPairHigh<Register>();
-  if (shift == 32) {
+  if (shift == 1) {
+    // This is just an addition.
+    __ addl(low, low);
+    __ adcl(high, high);
+  } else if (shift == 32) {
     // Shift by 32 is easy. High gets low, and low gets 0.
     codegen_->EmitParallelMoves(
         loc.ToLow(),

compiler/optimizing/instruction_simplifier.cc

diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index e79d4f4..46fad17 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -137,13 +137,25 @@
   HConstant* input_cst = instruction->GetConstantRight();
   HInstruction* input_other = instruction->GetLeastConstantLeft();
 
-  if ((input_cst != nullptr) && input_cst->IsZero()) {
-    // Replace code looking like
-    //    SHL dst, src, 0
-    // with
-    //    src
-    instruction->ReplaceWith(input_other);
-    instruction->GetBlock()->RemoveInstruction(instruction);
+  if (input_cst != nullptr) {
+    if (input_cst->IsZero()) {
+      // Replace code looking like
+      //    SHL dst, src, 0
+      // with
+      //    src
+      instruction->ReplaceWith(input_other);
+      instruction->GetBlock()->RemoveInstruction(instruction);
+    } else if (instruction->IsShl() && input_cst->IsOne()) {
+      // Replace Shl looking like
+      //    SHL dst, src, 1
+      // with
+      //    ADD dst, src, src
+      HAdd *add = new(GetGraph()->GetArena()) HAdd(instruction->GetType(),
+                                                   input_other,
+                                                   input_other);
+      instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, add);
+      RecordSimplification();
+    }
   }
 }