[llvm-commits] [llvm] r92426 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/load-cmp.ll
Chris Lattner
sabre at nondot.org
Sat Jan 2 13:50:25 PST 2010
Author: lattner
Date: Sat Jan 2 15:50:18 2010
New Revision: 92426
URL: http://llvm.org/viewvc/llvm-project?rev=92426&view=rev
Log:
Teach the table lookup optimization to generate range compares
when a consequtive sequence of elements all satisfies the
predicate. Like the double compare case, this generates better
code than the magic constant case and generalizes to more than
32/64 element array lookups.
Here are some examples where it triggers. From 403.gcc, most
accesses to the rtx_class array are handled, e.g.:
@rtx_class = constant [153 x i8] c"xxxxxmmmmmmmmxxxxxxxxxxxxmxxxxxxiiixxxxxxxxxxxxxxxxxxxooxooooooxxoooooox3x2c21c2222ccc122222ccccaaaaaa<<<<<<<<<<<<<<<<<<111111111111bbooxxxxxxxxxxcc2211x", align 32 ; <[153 x i8]*> [#uses=547]
%142 = icmp eq i8 %141, 105
@rtx_class = constant [153 x i8] c"xxxxxmmmmmmmmxxxxxxxxxxxxmxxxxxxiiixxxxxxxxxxxxxxxxxxxooxooooooxxoooooox3x2c21c2222ccc122222ccccaaaaaa<<<<<<<<<<<<<<<<<<111111111111bbooxxxxxxxxxxcc2211x", align 32 ; <[153 x i8]*> [#uses=543]
%165 = icmp eq i8 %164, 60
Also, most of the 59-element arrays (mode_class/rid_to_yy, etc)
optimized before are actually range compares. This lets 32-bit
machines optimize them.
400.perlbmk has stuff like this:
400.perlbmk: PL_regkind, even for 32-bit:
@PL_regkind = constant [62 x i8] c"\00\00\02\02\02\06\06\06\06\09\09\0B\0B\0D\0E\0E\0E\11\12\12\14\14\16\16\18\18\1A\1A\1C\1C\1E\1F !!!$$&'((((,-.///88886789:;8$", align 32 ; <[62 x i8]*> [#uses=4]
%811 = icmp ne i8 %810, 33
@PL_utf8skip = constant [256 x i8] c"\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\01\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\02\03\03\03\03\03\03\03\03\03\03\03\03\03\03\03\03\04\04\04\04\04\04\04\04\05\05\05\05\06\06\07\0D", align 32 ; <[256 x i8]*> [#uses=94]
%12 = icmp ult i8 %10, 2
etc.
Modified:
llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
llvm/trunk/test/Transforms/InstCombine/load-cmp.ll
Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=92426&r1=92425&r2=92426&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Sat Jan 2 15:50:18 2010
@@ -6053,6 +6053,14 @@
// form "i != 47 & i != 87". Same state transitions as for true elements.
int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
+ /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
+ /// define a state machine that triggers for ranges of values that the index
+ /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
+ /// This is -2 when undefined, -3 when overdefined, and otherwise the last
+ /// index in the range (inclusive). We use -2 for undefined here because we
+ /// use relative comparisons and don't want 0-1 to match -1.
+ int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
+
// MagicBitvector - This is a magic bitvector where we set a bit if the
// comparison is true for element 'i'. If there are 64 elements or less in
// the array, this will fully represent all the comparison results.
@@ -6067,7 +6075,15 @@
Init->getOperand(i),
CompareRHS, TD);
// If the result is undef for this element, ignore it.
- if (isa<UndefValue>(C)) continue;
+ if (isa<UndefValue>(C)) {
+ // Extend range state machines to cover this element in case there is an
+ // undef in the middle of the range.
+ if (TrueRangeEnd == (int)i-1)
+ TrueRangeEnd = i;
+ if (FalseRangeEnd == (int)i-1)
+ FalseRangeEnd = i;
+ continue;
+ }
// If we can't compute the result for any of the elements, we have to give
// up evaluating the entire conditional.
@@ -6077,32 +6093,54 @@
// update our state machines.
bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
- // State machine for single index comparison.
+ // State machine for single/double/range index comparison.
if (IsTrueForElt) {
// Update the TrueElement state machine.
if (FirstTrueElement == Undefined)
- FirstTrueElement = i;
- else if (SecondTrueElement == Undefined)
- SecondTrueElement = i;
- else
- SecondTrueElement = Overdefined;
+ FirstTrueElement = TrueRangeEnd = i; // First true element.
+ else {
+ // Update double-compare state machine.
+ if (SecondTrueElement == Undefined)
+ SecondTrueElement = i;
+ else
+ SecondTrueElement = Overdefined;
+
+ // Update range state machine.
+ if (TrueRangeEnd == (int)i-1)
+ TrueRangeEnd = i;
+ else
+ TrueRangeEnd = Overdefined;
+ }
} else {
// Update the FalseElement state machine.
if (FirstFalseElement == Undefined)
- FirstFalseElement = i;
- else if (SecondFalseElement == Undefined)
- SecondFalseElement = i;
- else
- SecondFalseElement = Overdefined;
+ FirstFalseElement = FalseRangeEnd = i; // First false element.
+ else {
+ // Update double-compare state machine.
+ if (SecondFalseElement == Undefined)
+ SecondFalseElement = i;
+ else
+ SecondFalseElement = Overdefined;
+
+ // Update range state machine.
+ if (FalseRangeEnd == (int)i-1)
+ FalseRangeEnd = i;
+ else
+ FalseRangeEnd = Overdefined;
+ }
}
+
// If this element is in range, update our magic bitvector.
if (i < 64 && IsTrueForElt)
MagicBitvector |= 1ULL << i;
- // If all of our states become overdefined, bail out early.
- if (i >= 64 && SecondTrueElement == Overdefined &&
- SecondFalseElement == Overdefined)
+ // If all of our states become overdefined, bail out early. Since the
+ // predicate is expensive, only check it every 8 elements. This is only
+ // really useful for really huge arrays.
+ if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
+ SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
+ FalseRangeEnd == Overdefined)
return 0;
}
@@ -6110,6 +6148,7 @@
// order the state machines in complexity of the generated code.
Value *Idx = GEP->getOperand(2);
+
// If the comparison is only true for one or two elements, emit direct
// comparisons.
if (SecondTrueElement != Overdefined) {
@@ -6150,6 +6189,37 @@
return BinaryOperator::CreateAnd(C1, C2);
}
+ // If the comparison can be replaced with a range comparison for the elements
+ // where it is true, emit the range check.
+ if (TrueRangeEnd != Overdefined) {
+ assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare");
+
+ // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
+ if (FirstTrueElement) {
+ Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
+ Idx = Builder->CreateAdd(Idx, Offs);
+ }
+
+ Value *End = ConstantInt::get(Idx->getType(),
+ TrueRangeEnd-FirstTrueElement+1);
+ return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
+ }
+
+ // False range check.
+ if (FalseRangeEnd != Overdefined) {
+ assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare");
+ // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
+ if (FirstFalseElement) {
+ Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
+ Idx = Builder->CreateAdd(Idx, Offs);
+ }
+
+ Value *End = ConstantInt::get(Idx->getType(),
+ FalseRangeEnd-FirstFalseElement);
+ return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
+ }
+
+
// If a 32-bit or 64-bit magic bitvector captures the entire comparison state
// of this load, replace it with computation that does:
// ((magic_cst >> i) & 1) != 0
@@ -6166,14 +6236,8 @@
return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
}
- // TODO: Range check
- // TODO: GEP 0, i, 4
// TODO: A[i]&4 == 0
-
- //errs() << "XFORM: " << *GV << "\n";
- //errs() << "\t" << *GEP << "\n";
- //errs() << "\t " << ICI << "\n\n\n\n";
-
+ // TODO: GEP 0, i, 4
return 0;
}
Modified: llvm/trunk/test/Transforms/InstCombine/load-cmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/load-cmp.ll?rev=92426&r1=92425&r2=92426&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/load-cmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/load-cmp.ll Sat Jan 2 15:50:18 2010
@@ -2,7 +2,8 @@
@G16 = internal constant [10 x i16] [i16 35, i16 82, i16 69, i16 81, i16 85,
i16 73, i16 82, i16 69, i16 68, i16 0]
- at GD = internal constant [3 x double] [double 1.0, double 4.0, double -20.0]
+ at GD = internal constant [6 x double]
+ [double -10.0, double 1.0, double 4.0, double 2.0, double -20.0, double -40.0]
define i1 @test1(i32 %X) {
%P = getelementptr [10 x i16]* @G16, i32 0, i32 %X
@@ -25,12 +26,12 @@
}
define i1 @test3(i32 %X) {
- %P = getelementptr [3 x double]* @GD, i32 0, i32 %X
+ %P = getelementptr [6 x double]* @GD, i32 0, i32 %X
%Q = load double* %P
%R = fcmp oeq double %Q, 1.0
ret i1 %R
; CHECK: @test3
-; CHECK-NEXT: %R = icmp eq i32 %X, 0
+; CHECK-NEXT: %R = icmp eq i32 %X, 1
; CHECK-NEXT: ret i1 %R
}
@@ -57,3 +58,25 @@
; CHECK-NEXT: %R = or i1
; CHECK-NEXT: ret i1 %R
}
+
+define i1 @test6(i32 %X) {
+ %P = getelementptr [6 x double]* @GD, i32 0, i32 %X
+ %Q = load double* %P
+ %R = fcmp ogt double %Q, 0.0
+ ret i1 %R
+; CHECK: @test6
+; CHECK-NEXT: add i32 %X, -1
+; CHECK-NEXT: %R = icmp ult i32 {{.*}}, 3
+; CHECK-NEXT: ret i1 %R
+}
+
+define i1 @test7(i32 %X) {
+ %P = getelementptr [6 x double]* @GD, i32 0, i32 %X
+ %Q = load double* %P
+ %R = fcmp olt double %Q, 0.0
+ ret i1 %R
+; CHECK: @test7
+; CHECK-NEXT: add i32 %X, -1
+; CHECK-NEXT: %R = icmp ugt i32 {{.*}}, 2
+; CHECK-NEXT: ret i1 %R
+}
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