[llvm] r242257 - [LoopUnrolling] Handle cast instructions.
Michael Zolotukhin
mzolotukhin at apple.com
Tue Jul 14 17:19:52 PDT 2015
Author: mzolotukhin
Date: Tue Jul 14 19:19:51 2015
New Revision: 242257
URL: http://llvm.org/viewvc/llvm-project?rev=242257&view=rev
Log:
[LoopUnrolling] Handle cast instructions.
During estimation of unrolling effect we should be able to propagate
constants through casts.
Differential Revision: http://reviews.llvm.org/D10207
Added:
llvm/trunk/test/Transforms/LoopUnroll/full-unroll-heuristics-cast.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp?rev=242257&r1=242256&r2=242257&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp Tue Jul 14 19:19:51 2015
@@ -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
Added: llvm/trunk/test/Transforms/LoopUnroll/full-unroll-heuristics-cast.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnroll/full-unroll-heuristics-cast.ll?rev=242257&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnroll/full-unroll-heuristics-cast.ll (added)
+++ llvm/trunk/test/Transforms/LoopUnroll/full-unroll-heuristics-cast.ll Tue Jul 14 19:19:51 2015
@@ -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"
+
+ at 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
+}
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