[ValueTracking] Add tests for checking whether `div`/`rem` is safe to speculate; NFC

[nikic]

The test cases would probably be simpler if this were using LICM.

llvm/test/Analysis/ValueTracking/speculate-div.ll

2 ↗

(On Diff #517806)

Should have mentioned this earlier, but please don't put tests into llvm/test/Analysis/ValueTracking, unless they use special analysis printers. Instead put them into the pass being tested, here llvm/test/Transforms/SimplifyCFG.

7 ↗

(On Diff #517806)

The function attributes shouldn't be needed.

[goldstein.w.n]

Move tests + remove unneeded attrs

[nikic]

What do you think about this test structure? https://llvm.godbolt.org/z/nMxMGoz1r Seems clearer to me than going through speculative hoisting.

[goldstein.w.n]

In D149422#4307697, @nikic wrote:

What do you think about this test structure? https://llvm.godbolt.org/z/nMxMGoz1r Seems clearer to me than going through speculative hoisting.

Sure, where would that test belong? simplifycfg still?
Edit: putting in Transform/LICM.

[goldstein.w.n]

Simplify tests + move to LICM

[nikic]

LGTM

llvm/test/Transforms/LICM/speculate-div.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=licm -S | FileCheck %s
+
+declare void @maythrow()
+declare void @use(i16)
+
+define void @sdiv_not_ok(i16 %n, i16 %xx) {
+; CHECK-LABEL: @sdiv_not_ok(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[X:%.*]] = or i16 [[XX:%.*]], 1
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i16 [[N:%.*]], [[X]]
+; CHECK-NEXT:    call void @use(i16 [[DIV]])
+; CHECK-NEXT:    br label [[LOOP]]
+;
+entry:
+  %x = or i16 %xx, 1
+  br label %loop
+loop:
+  call void @maythrow()
+  %div = sdiv i16 %n, %x
+  call void @use(i16 %div)
+  br label %loop
+}
+
+define void @srem_not_ok2(i16 %nn, i16 %x) {
+; CHECK-LABEL: @srem_not_ok2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[N:%.*]] = and i16 [[NN:%.*]], 1323
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[DIV:%.*]] = srem i16 [[N]], [[X:%.*]]
+; CHECK-NEXT:    call void @use(i16 [[DIV]])
+; CHECK-NEXT:    br label [[LOOP]]
+;
+entry:
+  %n = and i16 %nn, 1323
+  br label %loop
+loop:
+  call void @maythrow()
+  %div = srem i16 %n, %x
+  call void @use(i16 %div)
+  br label %loop
+}
+
+define void @sdiv_ok(i16 %n, i16 %xx) {
+; CHECK-LABEL: @sdiv_ok(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[XO:%.*]] = or i16 [[XX:%.*]], 1
+; CHECK-NEXT:    [[X:%.*]] = and i16 [[XO]], 123
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i16 [[N:%.*]], [[X]]
+; CHECK-NEXT:    call void @use(i16 [[DIV]])
+; CHECK-NEXT:    br label [[LOOP]]
+;
+entry:
+  %xo = or i16 %xx, 1
+  %x = and i16 %xo, 123
+  br label %loop
+loop:
+  call void @maythrow()
+  %div = sdiv i16 %n, %x
+  call void @use(i16 %div)
+  br label %loop
+}
+
+define void @srem_ok2(i16 %nn, i16 %xx) {
+; CHECK-LABEL: @srem_ok2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[N:%.*]] = and i16 [[NN:%.*]], 123
+; CHECK-NEXT:    [[X:%.*]] = or i16 [[XX:%.*]], 1
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[DIV:%.*]] = srem i16 [[N]], [[X]]
+; CHECK-NEXT:    call void @use(i16 [[DIV]])
+; CHECK-NEXT:    br label [[LOOP]]
+;
+entry:
+  %n = and i16 %nn, 123
+  %x = or i16 %xx, 1
+  br label %loop
+loop:
+  call void @maythrow()
+  %div = srem i16 %n, %x
+  call void @use(i16 %div)
+  br label %loop
+}
+
+define void @udiv_not_ok(i16 %n, i16 %xx) {
+; CHECK-LABEL: @udiv_not_ok(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[X:%.*]] = xor i16 [[XX:%.*]], 1
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[DIV:%.*]] = udiv i16 [[N:%.*]], [[X]]
+; CHECK-NEXT:    call void @use(i16 [[DIV]])
+; CHECK-NEXT:    br label [[LOOP]]
+;
+entry:
+  %x = xor i16 %xx, 1
+  br label %loop
+loop:
+  call void @maythrow()
+  %div = udiv i16 %n, %x
+  call void @use(i16 %div)
+  br label %loop
+}
+
+define void @udiv_ok(i16 %n, i16 %xx) {
+; CHECK-LABEL: @udiv_ok(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[X:%.*]] = or i16 [[XX:%.*]], 1
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[DIV:%.*]] = udiv i16 [[N:%.*]], [[X]]
+; CHECK-NEXT:    call void @use(i16 [[DIV]])
+; CHECK-NEXT:    br label [[LOOP]]
+;
+entry:
+  %x = or i16 %xx, 1
+  br label %loop
+loop:
+  call void @maythrow()
+  %div = udiv i16 %n, %x
+  call void @use(i16 %div)
+  br label %loop
+}