ART: Fix the simplifier for add/sub
Instruction simplifier for add/sub should not proceed with floats
because that might cause the incorrect behavior with signed zero.
Change-Id: If0c9bf3931bcbf96b0814f8605a86997aea37145
Signed-off-by: Serguei Katkov <serguei.i.katkov@intel.com>
diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index d391145..931a1c3 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -438,9 +438,14 @@
// ADD dst, src, 0
// with
// src
- instruction->ReplaceWith(input_other);
- instruction->GetBlock()->RemoveInstruction(instruction);
- return;
+ // Note that we cannot optimize `x + 0.0` to `x` for floating-point. When
+ // `x` is `-0.0`, the former expression yields `0.0`, while the later
+ // yields `-0.0`.
+ if (Primitive::IsIntegralType(instruction->GetType())) {
+ instruction->ReplaceWith(input_other);
+ instruction->GetBlock()->RemoveInstruction(instruction);
+ return;
+ }
}
HInstruction* left = instruction->GetLeft();
@@ -800,21 +805,24 @@
HConstant* input_cst = instruction->GetConstantRight();
HInstruction* input_other = instruction->GetLeastConstantLeft();
+ Primitive::Type type = instruction->GetType();
+ if (Primitive::IsFloatingPointType(type)) {
+ return;
+ }
+
if ((input_cst != nullptr) && input_cst->IsZero()) {
// Replace code looking like
// SUB dst, src, 0
// with
// src
+ // Note that we cannot optimize `x - 0.0` to `x` for floating-point. When
+ // `x` is `-0.0`, the former expression yields `0.0`, while the later
+ // yields `-0.0`.
instruction->ReplaceWith(input_other);
instruction->GetBlock()->RemoveInstruction(instruction);
return;
}
- Primitive::Type type = instruction->GetType();
- if (!Primitive::IsIntegralType(type)) {
- return;
- }
-
HBasicBlock* block = instruction->GetBlock();
ArenaAllocator* allocator = GetGraph()->GetArena();
diff --git a/test/474-fp-sub-neg/expected.txt b/test/474-fp-sub-neg/expected.txt
index e6ffe0d..1c15abb 100644
--- a/test/474-fp-sub-neg/expected.txt
+++ b/test/474-fp-sub-neg/expected.txt
@@ -1,2 +1,6 @@
-0.0
+0.0
+0.0
-0.0
+0.0
+0.0
diff --git a/test/474-fp-sub-neg/info.txt b/test/474-fp-sub-neg/info.txt
index eced93f..82effdb 100644
--- a/test/474-fp-sub-neg/info.txt
+++ b/test/474-fp-sub-neg/info.txt
@@ -1,5 +1,11 @@
Regression check for optimizing simplify instruction pass.
+
A pair (sub, neg) should not be transforemd to (sub) for
fp calculation because we can lose the sign of zero for
the following expression:
- ( A - B ) != B - A ; if B == A
+
+Addition or subtraction with fp zero should not be eliminated
+because:
+ -0.0 + 0.0 = 0.0
+ -0.0 - -0.0 = 0.0
diff --git a/test/474-fp-sub-neg/src/Main.java b/test/474-fp-sub-neg/src/Main.java
index e6bce67..c190e8e 100644
--- a/test/474-fp-sub-neg/src/Main.java
+++ b/test/474-fp-sub-neg/src/Main.java
@@ -24,6 +24,8 @@
}
System.out.println(f);
+ System.out.println(f + 0f);
+ System.out.println(f - (-0f));
}
public static void doubleTest() {
@@ -35,6 +37,8 @@
}
System.out.println(d);
+ System.out.println(d + 0f);
+ System.out.println(d - (-0f));
}
public static void main(String[] args) {
