StringBuilder append pattern for float/double.

Results for added benchmarks on blueline-userdebug with cpu
frequencies fxed at 1420800 (cpus 0-3; little) and 1459200
(cpus 4-7; big):
32-bit little (--variant=X32 --invoke-with 'taskset 0f')
  timeAppendStringAndDouble: ~1260ns -> ~970ns
  timeAppendStringAndFloat: ~1250ns -> ~940ns
  timeAppendStringAndHugeDouble: ~4700ns -> ~4690ns (noise)
  timeAppendStringAndHugeFloat: ~3400ns -> ~3300ns (noise)
  timeAppendStringDoubleStringAndFloat: ~1980ns -> ~1550ns
64-bit little (--variant=X64 --invoke-with 'taskset 0f')
  timeAppendStringAndDouble: ~1260ns -> ~970ns
  timeAppendStringAndFloat: ~1260ns -> ~940ns
  timeAppendStringAndHugeDouble: ~4700ns -> ~4800ns (noise)
  timeAppendStringAndHugeFloat: ~3300ns -> ~3400ns (noise)
  timeAppendStringDoubleStringAndFloat: ~1970ns -> ~1550ns
32-bit big (--variant=X32 --invoke-with 'taskset f0')
  timeAppendStringAndDouble: ~580ns -> ~450ns
  timeAppendStringAndFloat: ~590ns -> ~430ns
  timeAppendStringAndHugeDouble: ~2500ns -> ~2100ns (noise)
  timeAppendStringAndHugeFloat: ~1500ns -> ~1300ns (noise)
  timeAppendStringDoubleStringAndFloat: ~880ns -> ~730ns
64-bit big (--variant=X64 --invoke-with 'taskset f0')
  timeAppendStringAndDouble: ~590ns -> ~450ns
  timeAppendStringAndFloat: ~590ns -> ~430ns
  timeAppendStringAndHugeDouble: ~2300ns -> ~2300ns (noise)
  timeAppendStringAndHugeFloat: ~1500ns -> ~1300ns (noise)
  timeAppendStringDoubleStringAndFloat: ~870ns -> ~730ns

The `timeAppendStringAnd{Double,Float)` benchmarks show very
nice improvements, roughly 25% on both little and big cores.
The `timeAppendStringDoubleStringAndFloat` also shows decent
improvements, over 20% on little and over 15% on big cores.
(These benchmarks test the best-case scenario for "before"
as the StringBuilder's internal buffer is not reallocated.)

The `testAppendStringAndHuge{Double,Float}` results are too
noisy to draw any conclusions (especially on little cores
but there is still too much noise on big cores as well).

There are also small regressions for existing benchmarks
`timeAppend{LongStrings,StringAndInt,Strings}` but these
non-FP regressions may be mitigated after updating the
ThinLTO profile.

There is also an opportunity to optimize the calls back
to managed code for known shorty (in this change we use
"LD" and "LF") by using a dedicated stub instead of going
through the generic invoke stub.

Boot image size changes are insignificant (few matches).

Test: Added tests to 697-checker-string-append
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Test: testrunner.py --target --optimizing
Bug: 19575890
Change-Id: I9cf38c2d615a0a2b14255d18588a694d8870aae5

1 files changed, 74 insertions, 0 deletions

diff --git a/benchmark/stringbuilder-append/src/StringBuilderAppendBenchmark.java b/benchmark/stringbuilder-append/src/StringBuilderAppendBenchmark.java
index 1550e81bf7..d710e3409d 100644
--- a/benchmark/stringbuilder-append/src/StringBuilderAppendBenchmark.java
+++ b/benchmark/stringbuilder-append/src/StringBuilderAppendBenchmark.java
@@ -20,6 +20,10 @@ public class StringBuilderAppendBenchmark {
     public static String longString1 = "This is a long string 1";
     public static String longString2 = "This is a long string 2";
     public static int int1 = 42;
+    public static double double1 = 42.0;
+    public static double double2 = 1.0E308;
+    public static float float1 = 42.0f;
+    public static float float2 = 1.0E38f;
 
     public void timeAppendStrings(int count) {
         String s1 = string1;
@@ -59,4 +63,74 @@ public class StringBuilderAppendBenchmark {
             throw new AssertionError();
         }
     }
+
+    public void timeAppendStringAndDouble(int count) {
+        String s1 = string1;
+        double d1 = double1;
+        int sum = 0;
+        for (int i = 0; i < count; ++i) {
+            String result = s1 + d1;
+            sum += result.length();  // Make sure the append is not optimized away.
+        }
+        if (sum != count * (s1.length() + Double.toString(d1).length())) {
+            throw new AssertionError();
+        }
+    }
+
+    public void timeAppendStringAndHugeDouble(int count) {
+        String s1 = string1;
+        double d2 = double2;
+        int sum = 0;
+        for (int i = 0; i < count; ++i) {
+            String result = s1 + d2;
+            sum += result.length();  // Make sure the append is not optimized away.
+        }
+        if (sum != count * (s1.length() + Double.toString(d2).length())) {
+            throw new AssertionError();
+        }
+    }
+
+    public void timeAppendStringAndFloat(int count) {
+        String s1 = string1;
+        float f1 = float1;
+        int sum = 0;
+        for (int i = 0; i < count; ++i) {
+            String result = s1 + f1;
+            sum += result.length();  // Make sure the append is not optimized away.
+        }
+        if (sum != count * (s1.length() + Float.toString(f1).length())) {
+            throw new AssertionError();
+        }
+    }
+
+    public void timeAppendStringAndHugeFloat(int count) {
+        String s1 = string1;
+        float f2 = float2;
+        int sum = 0;
+        for (int i = 0; i < count; ++i) {
+            String result = s1 + f2;
+            sum += result.length();  // Make sure the append is not optimized away.
+        }
+        if (sum != count * (s1.length() + Float.toString(f2).length())) {
+            throw new AssertionError();
+        }
+    }
+
+    public void timeAppendStringDoubleStringAndFloat(int count) {
+        String s1 = string1;
+        String s2 = string2;
+        double d1 = double1;
+        float f1 = float1;
+        int sum = 0;
+        for (int i = 0; i < count; ++i) {
+            String result = s1 + d1 + s2 + f1;
+            sum += result.length();  // Make sure the append is not optimized away.
+        }
+        if (sum != count * (s1.length() +
+                            Double.toString(d1).length() +
+                            s2.length() +
+                            Float.toString(f1).length())) {
+            throw new AssertionError();
+        }
+    }
 }