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partial strength reduction for bit ops

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We had full constant eval of these already; this adds a bunch of
degenerate cases when one argument is known to be true or false.

Change-Id: Ic0535d8a99357947fd73bd9f719eec4645dc919d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/267243
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
This commit is contained in:
Mike Klein 2020-01-28 17:00:18 -06:00 committed by Skia Commit-Bot
parent 6f5441a2f6
commit faa34c536b
1 changed files with 14 additions and 0 deletions
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14
src/core/SkVM.cpp
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@ -730,6 +730,10 @@ namespace skvm {
I32 Builder::bit_and(I32 x, I32 y) {
int X,Y;
if (this->allImm(x.id,&X, y.id,&Y)) { return this->splat(X&Y); }
if (this->isImm(y.id, 0)) { return this->splat(0); } // (x & false) == false
if (this->isImm(x.id, 0)) { return this->splat(0); } // (false & y) == false
if (this->isImm(y.id,~0)) { return x; } // (x & true) == x
if (this->isImm(x.id,~0)) { return y; } // (true & y) == y
#if defined(SK_CPU_X86)
int imm;
if (this->allImm(y.id, &imm)) { return {this->push(Op::bit_and_imm, x.id,NA,NA, imm)}; }
@ -740,6 +744,10 @@ namespace skvm {
I32 Builder::bit_or(I32 x, I32 y) {
int X,Y;
if (this->allImm(x.id,&X, y.id,&Y)) { return this->splat(X|Y); }
if (this->isImm(y.id, 0)) { return x; } // (x | false) == x
if (this->isImm(x.id, 0)) { return y; } // (false | y) == y
if (this->isImm(y.id,~0)) { return this->splat(~0); } // (x | true) == true
if (this->isImm(x.id,~0)) { return this->splat(~0); } // (true | y) == true
#if defined(SK_CPU_X86)
int imm;
if (this->allImm(y.id, &imm)) { return {this->push(Op::bit_or_imm, x.id,NA,NA, imm)}; }
@ -750,6 +758,8 @@ namespace skvm {
I32 Builder::bit_xor(I32 x, I32 y) {
int X,Y;
if (this->allImm(x.id,&X, y.id,&Y)) { return this->splat(X^Y); }
if (this->isImm(y.id, 0)) { return x; } // (x ^ false) == x
if (this->isImm(x.id, 0)) { return y; } // (false ^ y) == y
#if defined(SK_CPU_X86)
int imm;
if (this->allImm(y.id, &imm)) { return {this->push(Op::bit_xor_imm, x.id,NA,NA, imm)}; }
@ -760,6 +770,9 @@ namespace skvm {
I32 Builder::bit_clear(I32 x, I32 y) {
int X,Y;
if (this->allImm(x.id,&X, y.id,&Y)) { return this->splat(X&~Y); }
if (this->isImm(y.id, 0)) { return x; } // (x & ~false) == x
if (this->isImm(y.id,~0)) { return this->splat(0); } // (x & ~true) == false
if (this->isImm(x.id, 0)) { return this->splat(0); } // (false & ~y) == false
#if defined(SK_CPU_X86)
int imm;
if (this->allImm(y.id, &imm)) { return this->bit_and(x, this->splat(~imm)); }
@ -770,6 +783,7 @@ namespace skvm {
I32 Builder::select(I32 x, I32 y, I32 z) {
int X,Y,Z;
if (this->allImm(x.id,&X, y.id,&Y, z.id,&Z)) { return this->splat(X?Y:Z); }
// TODO: some cases to reduce to bit_and when y == 0 or z == 0?
return {this->push(Op::select, x.id, y.id, z.id)};
}