Teach SCEV to handle more cases of 'and X, CST', specifically where CST is any number of contiguous 1 bits in a row, with any number of leading and trailing 0 bits.

Unfortunately, this in turn led to some lower quality SCEVs due to some different paths through expression simplification, so add getUDivExactExpr and use it. This fixes all instances of the problems that I found, but we can make that function smarter as necessary.

Merge test "xor-and.ll" into "and-xor.ll" since I needed to update it anyways. Test 'nsw-offset.ll' analyzes a little deeper, %n now gets a scev in terms of %no instead of a SCEVUnknown.

llvm-svn: 200203

4 files changed, 35 insertions, 15 deletions

diff --git a/llvm/test/Analysis/ScalarEvolution/and-xor.ll b/llvm/test/Analysis/ScalarEvolution/and-xor.ll
index 404ab91e269..ad636da4d4d 100644
--- a/llvm/test/Analysis/ScalarEvolution/and-xor.ll
+++ b/llvm/test/Analysis/ScalarEvolution/and-xor.ll
@@ -1,11 +1,27 @@
 ; RUN: opt < %s -scalar-evolution -analyze | FileCheck %s
 
+; CHECK-LABEL: @test1
 ; CHECK: -->  (zext
 ; CHECK: -->  (zext
 ; CHECK-NOT: -->  (zext
 
-define i32 @foo(i32 %x) {
+define i32 @test1(i32 %x) {
   %n = and i32 %x, 255
   %y = xor i32 %n, 255
   ret i32 %y
 }
+
+; ScalarEvolution shouldn't try to analyze %z into something like
+;   -->  (zext i4 (-1 + (-1 * (trunc i64 (8 * %x) to i4))) to i64)
+; or
+;   -->  (8 * (zext i1 (trunc i64 ((8 * %x) /u 8) to i1) to i64))
+
+; CHECK-LABEL: @test2
+; CHECK: -->  (8 * (zext i1 (trunc i64 %x to i1) to i64))
+
+define i64 @test2(i64 %x) {
+  %a = shl i64 %x, 3
+  %t = and i64 %a, 8
+  %z = xor i64 %t, 8
+  ret i64 %z
+}
diff --git a/llvm/test/Analysis/ScalarEvolution/fold.ll b/llvm/test/Analysis/ScalarEvolution/fold.ll
index 57006dd9bb4..84b657050c5 100644
--- a/llvm/test/Analysis/ScalarEvolution/fold.ll
+++ b/llvm/test/Analysis/ScalarEvolution/fold.ll
@@ -60,3 +60,20 @@ loop:
 exit:
   ret void
 }
+
+define void @test5(i32 %i) {
+; CHECK-LABEL: @test5
+  %A = and i32 %i, 1
+; CHECK: -->  (zext i1 (trunc i32 %i to i1) to i32)
+  %B = and i32 %i, 2
+; CHECK: -->  (2 * (zext i1 (trunc i32 (%i /u 2) to i1) to i32))
+  %C = and i32 %i, 63
+; CHECK: -->  (zext i6 (trunc i32 %i to i6) to i32)
+  %D = and i32 %i, 126
+; CHECK: -->  (2 * (zext i6 (trunc i32 (%i /u 2) to i6) to i32))
+  %E = and i32 %i, 64
+; CHECK: -->  (64 * (zext i1 (trunc i32 (%i /u 64) to i1) to i32))
+  %F = and i32 %i, -2147483648
+; CHECK: -->  (-2147483648 * (%i /u -2147483648))
+  ret void
+}
diff --git a/llvm/test/Analysis/ScalarEvolution/nsw-offset.ll b/llvm/test/Analysis/ScalarEvolution/nsw-offset.ll
index 8969a5ad4ce..88cdcf23d9e 100644
--- a/llvm/test/Analysis/ScalarEvolution/nsw-offset.ll
+++ b/llvm/test/Analysis/ScalarEvolution/nsw-offset.ll
@@ -73,5 +73,5 @@ return:                                           ; preds = %bb1.return_crit_edg
   ret void
 }
 
-; CHECK: Loop %bb: backedge-taken count is ((-1 + %n) /u 2)
+; CHECK: Loop %bb: backedge-taken count is ((-1 + (2 * (%no /u 2))) /u 2)
 ; CHECK: Loop %bb: max backedge-taken count is 1073741822
diff --git a/llvm/test/Analysis/ScalarEvolution/xor-and.ll b/llvm/test/Analysis/ScalarEvolution/xor-and.ll
deleted file mode 100644
index 2616ea928a4..00000000000
--- a/llvm/test/Analysis/ScalarEvolution/xor-and.ll
+++ /dev/null
@@ -1,13 +0,0 @@
-; RUN: opt < %s -scalar-evolution -analyze | FileCheck %s
-
-; ScalarEvolution shouldn't try to analyze %z into something like
-;   -->  (zext i4 (-1 + (-1 * (trunc i64 (8 * %x) to i4))) to i64)
-
-; CHECK: -->  (zext i4 (-8 + (trunc i64 (8 * %x) to i4)) to i64)
-
-define i64 @foo(i64 %x) {
-  %a = shl i64 %x, 3
-  %t = and i64 %a, 8
-  %z = xor i64 %t, 8
-  ret i64 %z
-}