[InstCombine] Add tests to demo generation of potentially illegal integer widths.

[bryant]

Summary

From D25913.

[spatel]

LGTM.

Note that I added a non-NUW test that would survive D25913 in rL285075.

When committing, I'd re-title this to something like "add tests for missing icmp + shl nuw fold".

[bryant]

In D25952#578756, @spatel wrote:

LGTM.

Note that I added a non-NUW test that would survive D25913 in rL285075.

Yes, I saw this commit while rebasing. I'll be posting my fix in a forthcoming Phab thread.

When committing, I'd re-title this to something like "add tests for missing icmp + shl nuw fold".

I don't have commit access, so you'll have to commit.

llvm/trunk/test/Transforms/InstCombine/icmp-shl-nuw.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+define i1 @icmp_ugt_32(i64) {
+; CHECK-LABEL: @icmp_ugt_32(
+; CHECK-NEXT:    [[C:%.*]] = shl nuw i64 %0, 32
+; CHECK-NEXT:    [[D:%.*]] = icmp ugt i64 [[C]], 4294967295
+; CHECK-NEXT:    ret i1 [[D]]
+;
+  %c = shl nuw i64 %0, 32
+  %d = icmp ugt i64 %c, 4294967295
+  ret i1 %d
+}
+
+define i1 @icmp_ule_64(i128) {
+; CHECK-LABEL: @icmp_ule_64(
+; CHECK-NEXT:    [[TMP2:%.*]] = trunc i128 %0 to i64
+; CHECK-NEXT:    [[D:%.*]] = icmp eq i64 [[TMP2]], 0
+; CHECK-NEXT:    ret i1 [[D]]
+;
+  %c = shl nuw i128 %0, 64
+  %d = icmp ule i128 %c, 18446744073709551615
+  ret i1 %d
+}
+
+define i1 @icmp_ugt_16(i64) {
+; CHECK-LABEL: @icmp_ugt_16(
+; CHECK-NEXT:    [[C:%.*]] = shl nuw i64 %0, 16
+; CHECK-NEXT:    [[D:%.*]] = icmp ugt i64 [[C]], 1048575
+; CHECK-NEXT:    ret i1 [[D]]
+;
+  %c = shl nuw i64 %0, 16
+  %d = icmp ugt i64 %c, 1048575 ; 0x0f_ffff
+  ret i1 %d
+}
+
+; FIXME: InstCombine ought not to emit the potentially illegal i48.
+define <2 x i1> @icmp_ule_16x2(<2 x i64>) {
+; CHECK-LABEL: @icmp_ule_16x2(
+; CHECK-NEXT:    [[TMP2:%.*]] = trunc <2 x i64> %0 to <2 x i48>
+; CHECK-NEXT:    [[D:%.*]] = icmp eq <2 x i48> [[TMP2]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[D]]
+;
+  %c = shl nuw <2 x i64> %0, <i64 16, i64 16>
+  %d = icmp ule <2 x i64> %c, <i64 65535, i64 65535>
+  ret <2 x i1> %d
+}
+
+define i1 @icmp_ult_8(i64) {
+; CHECK-LABEL: @icmp_ult_8(
+; CHECK-NEXT:    [[C:%.*]] = shl nuw i64 %0, 8
+; CHECK-NEXT:    [[D:%.*]] = icmp ult i64 [[C]], 4095
+; CHECK-NEXT:    ret i1 [[D]]
+;
+  %c = shl nuw i64 %0, 8
+  %d = icmp ult i64 %c, 4095 ; 0x0fff
+  ret i1 %d
+}
+
+define <2 x i1> @icmp_uge_8x2(<2 x i16>) {
+; CHECK-LABEL: @icmp_uge_8x2(
+; CHECK-NEXT:    [[C:%.*]] = shl nuw <2 x i16> %0, <i16 8, i16 8>
+; CHECK-NEXT:    [[D:%.*]] = icmp ugt <2 x i16> [[C]], <i16 4094, i16 4094>
+; CHECK-NEXT:    ret <2 x i1> [[D]]
+;
+  %c = shl nuw <2 x i16> %0, <i16 8, i16 8>
+  %d = icmp uge <2 x i16> %c, <i16 4095, i16 4095>
+  ret <2 x i1> %d
+}
+
+define <2 x i1> @icmp_ugt_16x2(<2 x i32>) {
+; CHECK-LABEL: @icmp_ugt_16x2(
+; CHECK-NEXT:    [[C:%.*]] = shl nuw <2 x i32> %0, <i32 16, i32 16>
+; CHECK-NEXT:    [[D:%.*]] = icmp ugt <2 x i32> [[C]], <i32 1048575, i32 1048575>
+; CHECK-NEXT:    ret <2 x i1> [[D]]
+;
+  %c = shl nuw <2 x i32> %0, <i32 16, i32 16>
+  %d = icmp ugt <2 x i32> %c, <i32 1048575, i32 1048575>
+  ret <2 x i1> %d
+}