[IndVarSimplify] Add AShr exact flags using induction variables ranges.

This adds exact flags to AShr/LShr flags where we can statically
prove it is valid using the range of induction variables. This
allows further optimisations to remove extra loads.

Differential Revision: https://reviews.llvm.org/D34207

llvm-svn: 307157

1 files changed, 84 insertions, 0 deletions

diff --git a/llvm/test/Transforms/IndVarSimplify/strengthen-overflow.ll b/llvm/test/Transforms/IndVarSimplify/strengthen-overflow.ll
index 2bafe96e1cc..6e0538e04d6 100644
--- a/llvm/test/Transforms/IndVarSimplify/strengthen-overflow.ll
+++ b/llvm/test/Transforms/IndVarSimplify/strengthen-overflow.ll
@@ -104,5 +104,89 @@ define i32 @test.unsigned.add.1(i32* %array, i32 %length, i32 %init) {
   ret i32 42
 }
 
+define hidden void @test.shl.exact.equal() {
+; CHECK-LABEL: @test.shl.exact.equal
+entry:
+  br label %for.body
+
+for.body:
+; CHECK-LABEL: for.body
+  %k.021 = phi i32 [ 1, %entry ], [ %inc, %for.body ]
+  %shl = shl i32 1, %k.021
+  %shr1 = ashr i32 %shl, 1
+; CHECK: %shr1 = ashr exact i32 %shl, 1
+  %shr2 = lshr i32 %shl, 1
+; CHECK: %shr2 = lshr exact i32 %shl, 1
+  %inc = add nuw nsw i32 %k.021, 1
+  %exitcond = icmp eq i32 %inc, 9
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}
+
+define hidden void @test.shl.exact.greater() {
+; CHECK-LABEL: @test.shl.exact.greater
+entry:
+  br label %for.body
+
+for.body:
+; CHECK-LABEL: for.body
+  %k.021 = phi i32 [ 3, %entry ], [ %inc, %for.body ]
+  %shl = shl i32 1, %k.021
+  %shr1 = ashr i32 %shl, 2
+; CHECK: %shr1 = ashr exact i32 %shl, 2
+  %shr2 = lshr i32 %shl, 2
+; CHECK: %shr2 = lshr exact i32 %shl, 2
+  %inc = add nuw nsw i32 %k.021, 1
+  %exitcond = icmp eq i32 %inc, 9
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}
+
+define hidden void @test.shl.exact.unbound(i32 %arg) {
+; CHECK-LABEL: @test.shl.exact.unbound
+entry:
+  br label %for.body
+
+for.body:
+; CHECK-LABEL: for.body
+  %k.021 = phi i32 [ 2, %entry ], [ %inc, %for.body ]
+  %shl = shl i32 1, %k.021
+  %shr1 = ashr i32 %shl, 2
+; CHECK: %shr1 = ashr exact i32 %shl, 2
+  %shr2 = lshr i32 %shl, 2
+; CHECK: %shr2 = lshr exact i32 %shl, 2
+  %inc = add nuw nsw i32 %k.021, 1
+  %exitcond = icmp eq i32 %inc, %arg
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}
+
+define hidden void @test.shl.nonexact() {
+; CHECK-LABEL: @test.shl.nonexact
+entry:
+  br label %for.body
+
+for.body:
+; CHECK-LABEL: for.body
+  %k.021 = phi i32 [ 2, %entry ], [ %inc, %for.body ]
+  %shl = shl i32 1, %k.021
+  %shr1 = ashr i32 %shl, 3
+; CHECK: %shr1 = ashr i32 %shl, 3
+  %shr2 = lshr i32 %shl, 3
+; CHECK: %shr2 = lshr i32 %shl, 3
+  %inc = add nuw nsw i32 %k.021, 1
+  %exitcond = icmp eq i32 %inc, 9
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}
+
 !0 = !{i32 0, i32 2}
 !1 = !{i32 0, i32 42}