[ValueTracking] Improve pointer offset computation for cases of same base

This patch improves the handling of pointer offset in GEP expressions where
one argument is the base pointer. isPointerOffset() is being used by memcpyopt
where current code synthesizes consecutive 32 bytes stores to one store and
two memset intrinsic calls. With this patch, we convert the stores to one
memset intrinsic.

Differential Revision: https://reviews.llvm.org/D67989

llvm-svn: 374454

1 files changed, 77 insertions, 0 deletions

diff --git a/llvm/test/Transforms/MemCpyOpt/store-to-memset.ll b/llvm/test/Transforms/MemCpyOpt/store-to-memset.ll
new file mode 100644
index 00000000000..59ed892b60e
--- /dev/null
+++ b/llvm/test/Transforms/MemCpyOpt/store-to-memset.ll
@@ -0,0 +1,77 @@
+; RUN: opt < %s -memcpyopt -S | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-grtev4-linux-gnu"
+
+define i8* @foo(i8* returned %0, i32 %1, i64 %2) {
+entry:
+  %3 = getelementptr inbounds i8, i8* %0, i64 %2
+  %4 = getelementptr inbounds i8, i8* %3, i64 -32
+  %vv = trunc i32 %1 to i8
+  store i8 %vv, i8* %4, align 1
+  %5 = getelementptr inbounds i8, i8* %4, i64 1
+  store i8 %vv, i8* %5, align 1
+  %6= getelementptr inbounds i8, i8* %4, i64 2
+  store i8 %vv, i8* %6, align 1
+  %7= getelementptr inbounds i8, i8* %4, i64 3
+  store i8 %vv, i8* %7, align 1
+  %8= getelementptr inbounds i8, i8* %4, i64 4
+  store i8 %vv, i8* %8, align 1
+  %9= getelementptr inbounds i8, i8* %4, i64 5
+  store i8 %vv, i8* %9, align 1
+  %10= getelementptr inbounds i8, i8* %4, i64 6
+  store i8 %vv, i8* %10, align 1
+  %11= getelementptr inbounds i8, i8* %4, i64 7
+  store i8 %vv, i8* %11, align 1
+  %12= getelementptr inbounds i8, i8* %4, i64 8
+  store i8 %vv, i8* %12, align 1
+  %13= getelementptr inbounds i8, i8* %4, i64 9
+  store i8 %vv, i8* %13, align 1
+  %14= getelementptr inbounds i8, i8* %4, i64 10
+  store i8 %vv, i8* %14, align 1
+  %15= getelementptr inbounds i8, i8* %4, i64 11
+  store i8 %vv, i8* %15, align 1
+  %16= getelementptr inbounds i8, i8* %4, i64 12
+  store i8 %vv, i8* %16, align 1
+  %17= getelementptr inbounds i8, i8* %4, i64 13
+  store i8 %vv, i8* %17, align 1
+  %18= getelementptr inbounds i8, i8* %4, i64 14
+  store i8 %vv, i8* %18, align 1
+  %19= getelementptr inbounds i8, i8* %4, i64 15
+  store i8 %vv, i8* %19, align 1
+  %20= getelementptr inbounds i8, i8* %4, i64 16
+  store i8 %vv, i8* %20, align 1
+  %21= getelementptr inbounds i8, i8* %20, i64 1
+  store i8 %vv, i8* %21, align 1
+  %22= getelementptr inbounds i8, i8* %20, i64 2
+  store i8 %vv, i8* %22, align 1
+  %23= getelementptr inbounds i8, i8* %20, i64 3
+  store i8 %vv, i8* %23, align 1
+  %24= getelementptr inbounds i8, i8* %20, i64 4
+  store i8 %vv, i8* %24, align 1
+  %25= getelementptr inbounds i8, i8* %20, i64 5
+  store i8 %vv, i8* %25, align 1
+  %26= getelementptr inbounds i8, i8* %20, i64 6
+  store i8 %vv, i8* %26, align 1
+  %27= getelementptr inbounds i8, i8* %20, i64 7
+  store i8 %vv, i8* %27, align 1
+  %28= getelementptr inbounds i8, i8* %20, i64 8
+  store i8 %vv, i8* %28, align 1
+  %29= getelementptr inbounds i8, i8* %20, i64 9
+  store i8 %vv, i8* %29, align 1
+  %30= getelementptr inbounds i8, i8* %20, i64 10
+  store i8 %vv, i8* %30, align 1
+  %31 = getelementptr inbounds i8, i8* %20, i64 11
+  store i8 %vv, i8* %31, align 1
+  %32 = getelementptr inbounds i8, i8* %20, i64 12
+  store i8 %vv, i8* %32, align 1
+  %33 = getelementptr inbounds i8, i8* %20, i64 13
+  store i8 %vv, i8* %33, align 1
+  %34 = getelementptr inbounds i8, i8* %20, i64 14
+  store i8 %vv, i8* %34, align 1
+  %35 = getelementptr inbounds i8, i8* %20, i64 15
+  store i8 %vv, i8* %35, align 1
+  ret i8* %0
+; CHECK-LABEL: @foo
+; CHECK: call void @llvm.memset.p0i8.i64(i8* align 1 %4, i8 %vv, i64 32, i1 false)
+}
+