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[LoopUnrolling] Handle cast instructions.

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During estimation of unrolling effect we should be able to propagate
constants through casts.

Differential Revision: http://reviews.llvm.org/D10207

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242257 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Zolotukhin 2015-07-15 00:19:51 +00:00
parent 6d27336681
commit 67ee52cf04
2 changed files with 109 additions and 0 deletions
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15
lib/Transforms/Scalar/LoopUnrollPass.cpp
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@ -436,6 +436,21 @@ private:
return true;
}
bool visitCastInst(CastInst &I) {
// Propagate constants through casts.
Constant *COp = dyn_cast<Constant>(I.getOperand(0));
if (!COp)
COp = SimplifiedValues.lookup(I.getOperand(0));
if (COp)
if (Constant *C =
ConstantExpr::getCast(I.getOpcode(), COp, I.getType())) {
SimplifiedValues[&I] = C;
return true;
}
return Base::visitCastInst(I);
}
};
} // namespace

94
test/Transforms/LoopUnroll/full-unroll-heuristics-cast.ll Normal file
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@ -0,0 +1,94 @@
; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=100 -unroll-dynamic-cost-savings-discount=1000 -unroll-threshold=10 -unroll-percent-dynamic-cost-saved-threshold=50 | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
@known_constant = internal unnamed_addr constant [10 x i32] [i32 0, i32 1, i32 0, i32 1, i32 0, i32 1, i32 0, i32 1, i32 0, i32 1], align 16
; We should be able to propagate constant data thru different types of casts.
; For example, in this test we have a load, which becomes constant after
; unrolling, which then is truncated to i8. Obviously, truncated value is also a
; constant, which can be used in the further simplifications.
;
; We expect this loop to be unrolled, because in this case load would become
; constant, which is 0 in many cases, and which, in its turn, helps to simplify
; following multiplication and addition. In total, unrolling should help to
; optimize ~60% of all instructions in this case.
;
; CHECK-LABEL: @const_load_trunc
; CHECK-NOT: br i1 %exitcond86.i, label %loop.end, label %loop
define i8 @const_load_trunc(i32* noalias nocapture readonly %src) {
entry:
br label %loop
loop: ; preds = %loop, %entry
%iv = phi i64 [ 0, %entry ], [ %inc, %loop ]
%r = phi i8 [ 0, %entry ], [ %add, %loop ]
%arrayidx = getelementptr inbounds i32, i32* %src, i64 %iv
%src_element = load i32, i32* %arrayidx, align 4
%array_const_idx = getelementptr inbounds [10 x i32], [10 x i32]* @known_constant, i64 0, i64 %iv
%const_array_element = load i32, i32* %array_const_idx, align 4
%x = trunc i32 %src_element to i8
%y = trunc i32 %const_array_element to i8
%mul = mul nsw i8 %x, %y
%add = add nsw i8 %mul, %r
%inc = add nuw nsw i64 %iv, 1
%exitcond86.i = icmp eq i64 %inc, 10
br i1 %exitcond86.i, label %loop.end, label %loop
loop.end: ; preds = %loop
%r.lcssa = phi i8 [ %r, %loop ]
ret i8 %r.lcssa
}
; The same test as before, but with ZEXT instead of TRUNC.
; CHECK-LABEL: @const_load_zext
; CHECK-NOT: br i1 %exitcond86.i, label %loop.end, label %loop
define i64 @const_load_zext(i32* noalias nocapture readonly %src) {
entry:
br label %loop
loop: ; preds = %loop, %entry
%iv = phi i64 [ 0, %entry ], [ %inc, %loop ]
%r = phi i64 [ 0, %entry ], [ %add, %loop ]
%arrayidx = getelementptr inbounds i32, i32* %src, i64 %iv
%src_element = load i32, i32* %arrayidx, align 4
%array_const_idx = getelementptr inbounds [10 x i32], [10 x i32]* @known_constant, i64 0, i64 %iv
%const_array_element = load i32, i32* %array_const_idx, align 4
%x = zext i32 %src_element to i64
%y = zext i32 %const_array_element to i64
%mul = mul nsw i64 %x, %y
%add = add nsw i64 %mul, %r
%inc = add nuw nsw i64 %iv, 1
%exitcond86.i = icmp eq i64 %inc, 10
br i1 %exitcond86.i, label %loop.end, label %loop
loop.end: ; preds = %loop
%r.lcssa = phi i64 [ %r, %loop ]
ret i64 %r.lcssa
}
; The same test as the first one, but with SEXT instead of TRUNC.
; CHECK-LABEL: @const_load_sext
; CHECK-NOT: br i1 %exitcond86.i, label %loop.end, label %loop
define i64 @const_load_sext(i32* noalias nocapture readonly %src) {
entry:
br label %loop
loop: ; preds = %loop, %entry
%iv = phi i64 [ 0, %entry ], [ %inc, %loop ]
%r = phi i64 [ 0, %entry ], [ %add, %loop ]
%arrayidx = getelementptr inbounds i32, i32* %src, i64 %iv
%src_element = load i32, i32* %arrayidx, align 4
%array_const_idx = getelementptr inbounds [10 x i32], [10 x i32]* @known_constant, i64 0, i64 %iv
%const_array_element = load i32, i32* %array_const_idx, align 4
%x = sext i32 %src_element to i64
%y = sext i32 %const_array_element to i64
%mul = mul nsw i64 %x, %y
%add = add nsw i64 %mul, %r
%inc = add nuw nsw i64 %iv, 1
%exitcond86.i = icmp eq i64 %inc, 10
br i1 %exitcond86.i, label %loop.end, label %loop
loop.end: ; preds = %loop
%r.lcssa = phi i64 [ %r, %loop ]
ret i64 %r.lcssa
}