[InstCombine][NFC] Add test to show missing fold for icmp ult/uge (shl %x, C2), C1.

[huihuiz]

Summary

'shl' inequality test

icmp ult/uge (shl %x, C2), C1 iff C1 is power of two

can be simplified as 'and' equality test

icmp eq/ne (and %x, (lshr -C1, C2)), 0.

[huihuiz]

minor fix of comments in the test file

[huihuiz]

remove test file for "shl-and-compare", as "shl-compare" test cases are sufficient.

[lebedev.ri]

llvm/test/Transforms/InstCombine/shl-unsigned-cmp-const.ll

83–87

Yeah, it's not really possible to ensure that those folds happen, the predicate is canonicalized.
I'd recommend to add those tests with predicate variants using vectors: https://godbolt.org/z/69dzCf
^ Looks like those aren't being canonicalized, at least right now.

[lebedev.ri]

Looks ok

[huihuiz]

Added vector test to check for predicate variance.
Canonicalization happens for ule -> ult , uge -> ugt

[lebedev.ri]

In D63670#1556548, @huihuiz wrote:

Added vector test to check for predicate variance.
Canonicalization happens for ule -> ult , uge -> ugt

Right, i forgot to enable instcombine in my godbolt link :)
Well then, i guess we can't have test coverage for that half of the fold :/

[huihuiz]

minor update for vector test,

for vector test

(X l<< 11) u<= 131071  , not 131072
}

similar for ugt test

sorry didn't catch this earlier

llvm/test/Transforms/InstCombine/shl-unsigned-cmp-const.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; Simplify 'shl' inequality test into 'and' equality test.
+;   (X l<< C2) u</u>= C1 iff C1 is power of 2 -> X & (-C1 l>> C2) ==/!= 0
+
+; Scalar tests
+
+; C2 Shift amount smaller than C1 trailing zeros.
+define i1 @scalar_i8_shl_ult_const_1(i8 %x) {
+; CHECK-LABEL: @scalar_i8_shl_ult_const_1(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i8 [[X:%.*]], 5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i8 [[SHL]], 64
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i8 %x, 5
+  %cmp = icmp ult i8 %shl, 64
+  ret i1 %cmp
+}
+
+; C2 Shift amount equal to C1 trailing zeros.
+define i1 @scalar_i8_shl_ult_const_2(i8 %x) {
+; CHECK-LABEL: @scalar_i8_shl_ult_const_2(
+; CHECK-NEXT:    [[SHL_MASK:%.*]] = and i8 [[X:%.*]], 3
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[SHL_MASK]], 0
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i8 %x, 6
+  %cmp = icmp ult i8 %shl, 64
+  ret i1 %cmp
+}
+
+; C2 Shift amount greater than C1 trailing zeros.
+define i1 @scalar_i8_shl_ult_const_3(i8 %x) {
+; CHECK-LABEL: @scalar_i8_shl_ult_const_3(
+; CHECK-NEXT:    [[SHL_MASK:%.*]] = and i8 [[X:%.*]], 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[SHL_MASK]], 0
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i8 %x, 7
+  %cmp = icmp ult i8 %shl, 64
+  ret i1 %cmp
+}
+
+; C2 Shift amount smaller than C1 trailing zeros.
+define i1 @scalar_i16_shl_ult_const(i16 %x) {
+; CHECK-LABEL: @scalar_i16_shl_ult_const(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i16 [[X:%.*]], 8
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i16 [[SHL]], 1024
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i16 %x, 8
+  %cmp = icmp ult i16 %shl, 1024
+  ret i1 %cmp
+}
+
+define i1 @scalar_i32_shl_ult_const(i32 %x) {
+; CHECK-LABEL: @scalar_i32_shl_ult_const(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i32 [[X:%.*]], 11
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i32 [[SHL]], 131072
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i32 %x, 11
+  %cmp = icmp ult i32 %shl, 131072
+  ret i1 %cmp
+}
+
+define i1 @scalar_i64_shl_ult_const(i64 %x) {
+; CHECK-LABEL: @scalar_i64_shl_ult_const(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i64 [[X:%.*]], 25
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i64 [[SHL]], 8589934592
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i64 %x, 25
+  %cmp = icmp ult i64 %shl, 8589934592
+  ret i1 %cmp
+}
+
+; Check 'uge' predicate
+define i1 @scalar_i8_shl_uge_const(i8 %x) {
+; CHECK-LABEL: @scalar_i8_shl_uge_const(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i8 [[X:%.*]], 5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i8 [[SHL]], 63
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i8 %x, 5
+  %cmp = icmp uge i8 %shl, 64
+  ret i1 %cmp
+}
+
+; Check 'ule' predicate
+define i1 @scalar_i8_shl_ule_const(i8 %x) {
+; CHECK-LABEL: @scalar_i8_shl_ule_const(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i8 [[X:%.*]], 5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i8 [[SHL]], 64
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i8 %x, 5
+  %cmp = icmp ule i8 %shl, 63
+  ret i1 %cmp
+}
+
+; Check 'ugt' predicate
+define i1 @scalar_i8_shl_ugt_const(i8 %x) {
+; CHECK-LABEL: @scalar_i8_shl_ugt_const(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i8 [[X:%.*]], 5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i8 [[SHL]], 63
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i8 %x, 5
+  %cmp = icmp ugt i8 %shl, 63
+  ret i1 %cmp
+}
+
+; Vector tests
+
+define <4 x i1> @vector_4xi32_shl_ult_const(<4 x i32> %x) {
+; CHECK-LABEL: @vector_4xi32_shl_ult_const(
+; CHECK-NEXT:    [[SHL:%.*]] = shl <4 x i32> [[X:%.*]], <i32 11, i32 11, i32 11, i32 11>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult <4 x i32> [[SHL]], <i32 131072, i32 131072, i32 131072, i32 131072>
+; CHECK-NEXT:    ret <4 x i1> [[CMP]]
+;
+  %shl = shl <4 x i32> %x, <i32 11, i32 11, i32 11, i32 11>
+  %cmp = icmp ult <4 x i32> %shl, <i32 131072, i32 131072, i32 131072, i32 131072>
+  ret <4 x i1> %cmp
+}
+
+define <4 x i1> @vector_4xi32_shl_ult_const_undef1(<4 x i32> %x) {
+; CHECK-LABEL: @vector_4xi32_shl_ult_const_undef1(
+; CHECK-NEXT:    [[SHL:%.*]] = shl <4 x i32> [[X:%.*]], <i32 11, i32 11, i32 undef, i32 11>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult <4 x i32> [[SHL]], <i32 131072, i32 131072, i32 131072, i32 131072>
+; CHECK-NEXT:    ret <4 x i1> [[CMP]]
+;
+  %shl = shl <4 x i32> %x, <i32 11, i32 11, i32 undef, i32 11>
+  %cmp = icmp ult <4 x i32> %shl, <i32 131072, i32 131072, i32 131072, i32 131072>
+  ret <4 x i1> %cmp
+}
+
+define <4 x i1> @vector_4xi32_shl_ult_const_undef2(<4 x i32> %x) {
+; CHECK-LABEL: @vector_4xi32_shl_ult_const_undef2(
+; CHECK-NEXT:    [[SHL:%.*]] = shl <4 x i32> [[X:%.*]], <i32 11, i32 11, i32 11, i32 11>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult <4 x i32> [[SHL]], <i32 131072, i32 131072, i32 131072, i32 undef>
+; CHECK-NEXT:    ret <4 x i1> [[CMP]]
+;
+  %shl = shl <4 x i32> %x, <i32 11, i32 11, i32 11, i32 11>
+  %cmp = icmp ult <4 x i32> %shl, <i32 131072, i32 131072, i32 131072, i32 undef>
+  ret <4 x i1> %cmp
+}
+
+define <4 x i1> @vector_4xi32_shl_ult_const_undef3(<4 x i32> %x) {
+; CHECK-LABEL: @vector_4xi32_shl_ult_const_undef3(
+; CHECK-NEXT:    [[SHL:%.*]] = shl <4 x i32> [[X:%.*]], <i32 11, i32 11, i32 undef, i32 11>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult <4 x i32> [[SHL]], <i32 undef, i32 131072, i32 131072, i32 131072>
+; CHECK-NEXT:    ret <4 x i1> [[CMP]]
+;
+  %shl = shl <4 x i32> %x, <i32 11, i32 11, i32 undef, i32 11>
+  %cmp = icmp ult <4 x i32> %shl, <i32 undef, i32 131072, i32 131072, i32 131072>
+  ret <4 x i1> %cmp
+}
+
+; Extra use
+
+; Not simplified
+define i1 @scalar_i8_shl_ult_const_extra_use_shl(i8 %x, i8* %p) {
+; CHECK-LABEL: @scalar_i8_shl_ult_const_extra_use_shl(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i8 [[X:%.*]], 5
+; CHECK-NEXT:    store i8 [[SHL]], i8* [[P:%.*]], align 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i8 [[SHL]], 64
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i8 %x, 5
+  store i8 %shl, i8* %p
+  %cmp = icmp ult i8 %shl, 64
+  ret i1 %cmp
+}
+
+; Negative tests
+
+; Check 'slt' predicate
+define i1 @scalar_i8_shl_slt_const(i8 %x) {
+; CHECK-LABEL: @scalar_i8_shl_slt_const(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i8 [[X:%.*]], 5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i8 [[SHL]], 64
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i8 %x, 5
+  %cmp = icmp slt i8 %shl, 64
+  ret i1 %cmp
+}
+
+define i1 @scalar_i8_shl_ugt_const_not_power_of_2(i8 %x) {
+; CHECK-LABEL: @scalar_i8_shl_ugt_const_not_power_of_2(
+; CHECK-NEXT:    [[SHL:%.*]] = shl i8 [[X:%.*]], 5
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i8 [[SHL]], 66
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shl = shl i8 %x, 5
+  %cmp = icmp ugt i8 %shl, 66
+  ret i1 %cmp
+}