Revert "Revert r236894 "[BasicAA] Fix zext & sext handling""

r236894 caused PR23626 (Clang miscompiles webkit's base64 decoder), and was
reverted in r237984. This reapplies the patch with an additional test case for
PR23626 and the associated fix (both scales and offsets in the
BasicAliasAnalysis::constantOffsetHeuristic should initially be zero).

Patch by Nick White, thanks!

llvm-svn: 241981

2 files changed, 197 insertions, 0 deletions

diff --git a/llvm/test/Analysis/BasicAA/bug.23540.ll b/llvm/test/Analysis/BasicAA/bug.23540.ll
new file mode 100644
index 00000000000..f693bcf73cd
--- /dev/null
+++ b/llvm/test/Analysis/BasicAA/bug.23540.ll
@@ -0,0 +1,17 @@
+; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@c = external global i32
+
+; CHECK-LABEL: f
+; CHECK: PartialAlias: i32* %arrayidx, i32* %arrayidx6
+define void @f() {
+  %idxprom = zext i32 undef to i64
+  %add4 = add i32 0, 1
+  %idxprom5 = zext i32 %add4 to i64
+  %arrayidx6 = getelementptr inbounds i32, i32* @c, i64 %idxprom5
+  %arrayidx = getelementptr inbounds i32, i32* @c, i64 %idxprom
+  ret void
+}
+
diff --git a/llvm/test/Analysis/BasicAA/q.bad.ll b/llvm/test/Analysis/BasicAA/q.bad.ll
new file mode 100644
index 00000000000..f2de6a76c5e
--- /dev/null
+++ b/llvm/test/Analysis/BasicAA/q.bad.ll
@@ -0,0 +1,180 @@
+; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "thumbv7--linux-gnueabi"
+
+; CHECK-LABEL: test_zext_sext_amounts255
+; CHECK: NoAlias: i8* %a, i8* %b
+define void @test_zext_sext_amounts255(i8* %mem) {
+  %sext.1 = sext i8 255 to i16
+  %sext.zext.1 = zext i16 %sext.1 to i64
+  %sext.2 = sext i8 255 to i32
+  %sext.zext.2 = zext i32 %sext.2 to i64
+  %a = getelementptr inbounds i8, i8* %mem, i64 %sext.zext.1
+  %b = getelementptr inbounds i8, i8* %mem, i64 %sext.zext.2
+  ret void
+}
+
+; CHECK-LABEL: test_zext_sext_amounts
+; CHECK: PartialAlias: i8* %a, i8* %b
+; %a and %b only PartialAlias as, although they're both zext(sext(%num)) they'll extend the sign by a different
+; number of bits before zext-ing the remainder.
+define void @test_zext_sext_amounts(i8* %mem, i8 %num) {
+  %sext.1 = sext i8 %num to i16
+  %sext.zext.1 = zext i16 %sext.1 to i64
+  %sext.2 = sext i8 %num to i32
+  %sext.zext.2 = zext i32 %sext.2 to i64
+  %a = getelementptr inbounds i8, i8* %mem, i64 %sext.zext.1
+  %b = getelementptr inbounds i8, i8* %mem, i64 %sext.zext.2
+  ret void
+}
+
+; CHECK-LABEL: based_on_pr18068
+; CHECK: NoAlias: i8* %a, i8* %b
+; CHECK: NoAlias: i8* %a, i8* %c
+define void @based_on_pr18068(i32 %loaded, i8* %mem) {
+  %loaded.64 = zext i32 %loaded to i64
+  %add1 = add i32 %loaded, -1 ; unsigned wraps unless %loaded == 0
+  %add1.64 = zext i32 %add1 to i64 ; is zext(%loaded) always != zext(%loaded - 1)? Yes -> NoAlias
+  %sub1 = sub i32 %loaded, 1 ; unsigned wraps iff %loaded == 0
+  %sub1.64 = zext i32 %sub1 to i64 ; is zext(%loaded) always != zext(%loaded - 1)? Yes -> NoAlias
+  %a = getelementptr inbounds i8, i8* %mem, i64 %loaded.64
+  %b = getelementptr inbounds i8, i8* %mem, i64 %add1.64
+  %c = getelementptr inbounds i8, i8* %mem, i64 %sub1.64
+  ret void
+}
+
+; CHECK-LABEL: test_path_dependence
+; CHECK: PartialAlias: i8* %a, i8* %b
+; CHECK: MustAlias: i8* %a, i8* %c
+; CHECK: PartialAlias: i8* %a, i8* %d
+define void @test_path_dependence(i32 %p, i8* %mem) {
+  %p.minus1 = add i32 %p, -1 ; this will always unsigned-wrap, unless %p == 0
+  %p.minus1.64 = zext i32 %p.minus1 to i64
+  %p.64.again = add i64 %p.minus1.64, 1 ; either %p (if we wrapped) or 4294967296 (if we didn't)
+
+  %p.nsw.nuw.minus1 = sub nsw nuw i32 %p, 1 ; as nuw we know %p >= 1, and as nsw %p <=   2147483647
+  %p.nsw.nuw.minus1.64 = zext i32 %p.nsw.nuw.minus1 to i64
+  %p.nsw.nuw.64.again = add nsw nuw i64 %p.nsw.nuw.minus1.64, 1 ; ...so always exactly %p
+
+  %p.nsw.minus1 = sub nsw i32 %p, 1 ; only nsw, so can only guarantee %p != 0x10000000
+  %p.nsw.minus1.64 = zext i32 %p.nsw.minus1 to i64 ; when %p > 0x10000000 (ie <= 0 as a signed number) then the zext will make this a huge positive number
+  %p.nsw.64.again = add nsw i64 %p.nsw.minus1.64, 1 ; ...and so this is very much != %p
+
+  %p.64 = zext i32 %p to i64
+  %a = getelementptr inbounds i8, i8* %mem, i64 %p.64
+  %b = getelementptr inbounds i8, i8* %mem, i64 %p.64.again
+  %c = getelementptr inbounds i8, i8* %mem, i64 %p.nsw.nuw.64.again
+  %d = getelementptr inbounds i8, i8* %mem, i64 %p.nsw.64.again
+  ret void
+}
+
+; CHECK-LABEL: test_zext_sext_255
+; CHECK: NoAlias: i8* %a, i8* %b
+define void @test_zext_sext_255(i8* %mem) {
+  %zext.255 = zext i8 255 to i16 ; 0x00FF
+  %sext.255 = sext i8 255 to i16 ; 0xFFFF
+  %zext.sext.255 = zext i16 %sext.255 to i32 ; 0x0000FFFF
+  %sext.zext.255 = sext i16 %zext.255 to i32 ; 0x000000FF
+  %zext.zext.sext.255 = zext i32 %zext.sext.255 to i64
+  %zext.sext.zext.255 = zext i32 %sext.zext.255 to i64
+  %a = getelementptr inbounds i8, i8* %mem, i64 %zext.zext.sext.255
+  %b = getelementptr inbounds i8, i8* %mem, i64 %zext.sext.zext.255
+  ret void
+}
+
+; CHECK-LABEL: test_zext_sext_num
+; CHECK: PartialAlias: i8* %a, i8* %b
+; %a and %b NoAlias if %num == 255 (see @test_zext_sext_255), but %a and %b NoAlias for other values of %num (e.g. 0)
+define void @test_zext_sext_num(i8* %mem, i8 %num) {
+  %zext.num = zext i8 %num to i16
+  %sext.num = sext i8 %num to i16
+  %zext.sext.num = zext i16 %sext.num to i32
+  %sext.zext.num = sext i16 %zext.num to i32
+  %zext.zext.sext.num = zext i32 %zext.sext.num to i64
+  %zext.sext.zext.num = zext i32 %sext.zext.num to i64
+  %a = getelementptr inbounds i8, i8* %mem, i64 %zext.zext.sext.num
+  %b = getelementptr inbounds i8, i8* %mem, i64 %zext.sext.zext.num
+  ret void
+}
+
+; CHECK-LABEL: uncompressStream
+; CHECK: MustAlias:  i8* %a, i8* %b
+; CHECK: NoAlias:  i8* %a, i8* %c
+define void @uncompressStream(i8* %mem) {
+  %zext.255 = zext i8 255 to i32
+  %sext.255 = sext i8 255 to i32
+  %a = getelementptr inbounds i8, i8* %mem, i32 255
+  %b = getelementptr inbounds i8, i8* %mem, i32 %zext.255
+  %c = getelementptr inbounds i8, i8* %mem, i32 %sext.255
+  ret void
+}
+
+; CHECK-LABEL: constantOffsetHeuristic_i3_i32
+; CHECK: NoAlias:  i32* %a, i32* %b
+; CHECK: NoAlias:  i32* %a, i32* %c
+; CHECK: NoAlias:  i32* %b, i32* %c
+define void @constantOffsetHeuristic_i3_i32(i32* %mem, i3 %val) {
+  %zext.plus.7 = add nsw i3 %val, 7
+  %zext.plus.4 = add nsw i3 %val, 4
+  %zext.val = zext i3 %val to i32
+  %zext.4 = zext i3 %zext.plus.4 to i32
+  %zext.7 = zext i3 %zext.plus.7 to i32
+  %a = getelementptr inbounds i32, i32* %mem, i32 %zext.4
+  %b = getelementptr inbounds i32, i32* %mem, i32 %zext.7
+  %c = getelementptr inbounds i32, i32* %mem, i32 %zext.val
+  ret void
+}
+
+; CHECK-LABEL: constantOffsetHeuristic_i8_i32
+; CHECK: NoAlias:  i32* %a, i32* %b
+; CHECK: NoAlias:  i32* %a, i32* %c
+; CHECK: NoAlias:  i32* %b, i32* %c
+define void @constantOffsetHeuristic_i8_i32(i32* %mem, i8 %val) {
+  %zext.plus.7 = add nsw i8 %val, 7
+  %zext.plus.4 = add nsw i8 %val, 4
+  %zext.val = zext i8 %val to i32
+  %zext.4 = zext i8 %zext.plus.4 to i32
+  %zext.7 = zext i8 %zext.plus.7 to i32
+  %a = getelementptr inbounds i32, i32* %mem, i32 %zext.4
+  %b = getelementptr inbounds i32, i32* %mem, i32 %zext.7
+  %c = getelementptr inbounds i32, i32* %mem, i32 %zext.val
+  ret void
+}
+
+; CHECK-LABEL: constantOffsetHeuristic_i3_i8
+; CHECK: PartialAlias:  i32* %a, i32* %b
+; CHECK: NoAlias:  i32* %a, i32* %c
+; CHECK: PartialAlias:  i32* %b, i32* %c
+define void @constantOffsetHeuristic_i3_i8(i8* %mem, i3 %val) {
+  %zext.plus.7 = add nsw i3 %val, 7
+  %zext.plus.4 = add nsw i3 %val, 4
+  %zext.val = zext i3 %val to i32
+  %zext.4 = zext i3 %zext.plus.4 to i32
+  %zext.7 = zext i3 %zext.plus.7 to i32
+  %a.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.4
+  %b.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.7
+  %c.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.val
+  %a = bitcast i8* %a.8 to i32*
+  %b = bitcast i8* %b.8 to i32*
+  %c = bitcast i8* %c.8 to i32*
+  ret void
+}
+
+; CHECK-LABEL: constantOffsetHeuristic_i8_i8
+; CHECK: PartialAlias:  i32* %a, i32* %b
+; CHECK: NoAlias:  i32* %a, i32* %c
+; CHECK: NoAlias:  i32* %b, i32* %c
+define void @constantOffsetHeuristic_i8_i8(i8* %mem, i8 %val) {
+  %zext.plus.7 = add nsw i8 %val, 7
+  %zext.plus.4 = add nsw i8 %val, 4
+  %zext.val = zext i8 %val to i32
+  %zext.4 = zext i8 %zext.plus.4 to i32
+  %zext.7 = zext i8 %zext.plus.7 to i32
+  %a.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.4
+  %b.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.7
+  %c.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.val
+  %a = bitcast i8* %a.8 to i32*
+  %b = bitcast i8* %b.8 to i32*
+  %c = bitcast i8* %c.8 to i32*
+  ret void
+}