[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242257 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopUnrollPass.cpp b/lib/Transforms/Scalar/LoopUnrollPass.cpp
index d78db6c369b3520d754ebfbc2b859db806ebc3d8..ff1acc1f5795db95486813511c3fbc60b0a39932 100644 (file)
--- a/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -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
 

diff --git a/test/Transforms/LoopUnroll/full-unroll-heuristics-cast.ll b/test/Transforms/LoopUnroll/full-unroll-heuristics-cast.ll
new file mode 100644 (file)
index 0000000..1d4eaef
--- /dev/null
+++ b/test/Transforms/LoopUnroll/full-unroll-heuristics-cast.ll
@@ -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
+}