Reviewers: Sven Panne,
Message:
PTAL
Description:
[arm] Fix UBFX detection.
Please review this at https://codereview.chromium.org/725063002/
Base URL: https://chromium.googlesource.com/v8/v8.git@master
Affected files (+19, -11 lines):
M src/compiler/arm/instruction-selector-arm.cc
Index: src/compiler/arm/instruction-selector-arm.cc
diff --git a/src/compiler/arm/instruction-selector-arm.cc
b/src/compiler/arm/instruction-selector-arm.cc
index
8fa6f24300165e838ca895f08f543c56de54a8df..24168cc98e1225e71dbf14e19c94fb93f2ca322a
100644
--- a/src/compiler/arm/instruction-selector-arm.cc
+++ b/src/compiler/arm/instruction-selector-arm.cc
@@ -368,6 +368,16 @@ void EmitBic(InstructionSelector* selector, Node*
node, Node* left,
g.UseRegister(right));
}
+
+void EmitUbfx(InstructionSelector* selector, Node* node, Node* left,
+ uint32_t lsb, uint32_t width) {
+ DCHECK_LE(1, width);
+ DCHECK_LE(width, 32 - lsb);
+ ArmOperandGenerator g(selector);
+ selector->Emit(kArmUbfx, g.DefineAsRegister(node), g.UseRegister(left),
+ g.TempImmediate(lsb), g.TempImmediate(width));
+}
+
} // namespace
@@ -398,15 +408,16 @@ void InstructionSelector::VisitWord32And(Node* node) {
if (m.left().IsWord32Shr()) {
Int32BinopMatcher mleft(m.left().node());
if (mleft.right().IsInRange(0, 31)) {
- Emit(kArmUbfx, g.DefineAsRegister(node),
- g.UseRegister(mleft.left().node()),
- g.UseImmediate(mleft.right().node()),
g.TempImmediate(width));
- return;
+ // UBFX cannot extract bits past the register size, however since
+ // shifting the original value would have introduced some zeros
we can
+ // still use UBFX with a smaller mask and the remaining bits
will be
+ // zeros.
+ uint32_t const lsb = mleft.right().Value();
+ return EmitUbfx(this, node, mleft.left().node(), lsb,
+ std::min(width, 32 - lsb));
}
}
- Emit(kArmUbfx, g.DefineAsRegister(node),
g.UseRegister(m.left().node()),
- g.TempImmediate(0), g.TempImmediate(width));
- return;
+ return EmitUbfx(this, node, m.left().node(), 0, width);
}
// Try to interpret this AND as BIC.
if (g.CanBeImmediate(~value)) {
@@ -523,10 +534,7 @@ void InstructionSelector::VisitWord32Shr(Node* node) {
uint32_t msb = base::bits::CountLeadingZeros32(value);
if (msb + width + lsb == 32) {
DCHECK_EQ(lsb, base::bits::CountTrailingZeros32(value));
- Emit(kArmUbfx, g.DefineAsRegister(node),
- g.UseRegister(mleft.left().node()), g.TempImmediate(lsb),
- g.TempImmediate(width));
- return;
+ return EmitUbfx(this, node, mleft.left().node(), lsb, width);
}
}
}
--
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