Implement more aggressive folding of add operand lists when

they contain multiplications of constants with add operations.
This helps simplify several kinds of things; in particular it
helps simplify expressions like ((-1 * (%a + %b)) + %a) to %b,
as expressions like this often come up in loop trip count
computations.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73361 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/IndVarSimplify/pointer.ll

@@ -0,0 +1,38 @@
+; RUN: llvm-as < %s | opt -indvars | llvm-dis > %t
+; RUN: grep {%exitcond = icmp eq i64 %indvar.next, %n} %t
+; RUN: grep {getelementptr i8\\* %A, i64 %indvar} %t
+; RUN: grep getelementptr %t | count 1
+; RUN: grep add %t | count 1
+; RUN: not grep scevgep %t
+; RUN: not grep ptrtoint %t
+
+; Indvars should be able to expand the pointer-arithmetic
+; IV into an integer IV indexing into a simple getelementptr.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64"
+
+define void @foo(i8* %A, i64 %n) nounwind {
+entry:
+	%0 = icmp eq i64 %n, 0		; <i1> [#uses=1]
+	br i1 %0, label %return, label %bb.nph
+
+bb.nph:		; preds = %entry
+	%1 = getelementptr i8* %A, i64 %n		; <i8*> [#uses=1]
+	br label %bb
+
+bb:		; preds = %bb1, %bb.nph
+	%q.01 = phi i8* [ %2, %bb1 ], [ %A, %bb.nph ]		; <i8*> [#uses=2]
+	store i8 0, i8* %q.01, align 1
+	%2 = getelementptr i8* %q.01, i64 1		; <i8*> [#uses=2]
+	br label %bb1
+
+bb1:		; preds = %bb
+	%3 = icmp eq i8* %1, %2		; <i1> [#uses=1]
+	br i1 %3, label %bb1.return_crit_edge, label %bb
+
+bb1.return_crit_edge:		; preds = %bb1
+	br label %return
+
+return:		; preds = %bb1.return_crit_edge, %entry
+	ret void
+}