Teach InstCombine's ComputeMaskedBits to handle pointer expressions

in addition to integer expressions. Rewrite GetOrEnforceKnownAlignment
as a ComputeMaskedBits problem, moving all of its special alignment
knowledge to ComputeMaskedBits as low-zero-bits knowledge.

Also, teach ComputeMaskedBits a few basic things about Mul and PHI
instructions.

This improves ComputeMaskedBits-based simplifications in a few cases,
but more noticeably it significantly improves instcombine's alignment
detection for loads, stores, and memory intrinsics.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49492 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 30 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/align-addr.ll b/test/Transforms/InstCombine/align-addr.ll
new file mode 100644
index 0000000..a05c513
--- /dev/null
+++ b/test/Transforms/InstCombine/align-addr.ll
@@ -0,0 +1,30 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {align 16} | count 1
+
+; Instcombine should be able to prove vector alignment in the
+; presence of a few mild address computation tricks.
+
+define void @foo(i8* %b, i64 %n, i64 %u, i64 %y) nounwind  {
+entry:
+  %c = ptrtoint i8* %b to i64
+  %d = and i64 %c, -16
+  %e = inttoptr i64 %d to double*
+  %v = mul i64 %u, 2
+  %z = and i64 %y, -2
+  %t1421 = icmp eq i64 %n, 0
+  br i1 %t1421, label %return, label %bb
+
+bb:
+  %i = phi i64 [ %indvar.next, %bb ], [ 20, %entry ]
+  %j = mul i64 %i, %v
+  %h = add i64 %j, %z
+  %t8 = getelementptr double* %e, i64 %h
+  %p = bitcast double* %t8 to <2 x double>*
+  store <2 x double><double 0.0, double 0.0>, <2 x double>* %p, align 8
+  %indvar.next = add i64 %i, 1
+  %exitcond = icmp eq i64 %indvar.next, %n
+  br i1 %exitcond, label %return, label %bb
+
+return:
+  ret void
+}
+