[llvm] [CorrelatedValuePropagation] Fold calls to UCMP/SCMP when we know that ranges of operands do not overlap (PR #97235)

[via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=correlated-propagation -S | FileCheck %s
+
+; If nothing is known we can't change anything
+define i8 @ucmp_0(i32 %x, i32 %y) {
+  %1 = call i8 @llvm.ucmp(i32 %x, i32 %y)
+  ret i8 %1
+}
+
+define i8 @scmp_0(i32 %x, i32 %y) {
+  %1 = call i8 @llvm.scmp(i32 %x, i32 %y)
+  ret i8 %1
+}
+
+; If we know that range of LHS < range of RHS then return -1
+define i8 @ucmp_1(i32 %x, i32 %y) {
+  ; X is within [4, 8)
+  %cond1 = icmp uge i32 %x, 4
+  call void @llvm.assume(i1 %cond1)
+  %cond2 = icmp ult i32 %x, 8
+  call void @llvm.assume(i1 %cond2)
+  ; Y is within [8, +INF)
+  %cond3 = icmp uge i32 %y, 8
+  call void @llvm.assume(i1 %cond3)
+
+  %1 = call i8 @llvm.ucmp(i32 %x, i32 %y)
+  ret i8 %1
+}
+
+define i8 @scmp_1(i32 %x, i32 %y) {
+  ; X is within [-5, 3)
+  %cond1 = icmp sge i32 %x, -5
+  call void @llvm.assume(i1 %cond1)
+  %cond2 = icmp slt i32 %x, 3
+  call void @llvm.assume(i1 %cond2)
+  ; Y is within [3, +INF)
+  %cond3 = icmp sge i32 %y, 3
+  call void @llvm.assume(i1 %cond3)
+
+  %1 = call i8 @llvm.scmp(i32 %x, i32 %y)
+  ret i8 %1
+}
+
+; If we know that range of LHS > range of RHS then return 1
+define i8 @ucmp_2(i32 %x, i32 %y) {
+  ; X is within [4, +INF)
+  %cond1 = icmp uge i32 %x, 4
+  call void @llvm.assume(i1 %cond1)
+  ; Y is within [0, 4)
+  %cond2 = icmp ult i32 %y, 4
+  call void @llvm.assume(i1 %cond2)
+
+  %1 = call i8 @llvm.ucmp(i32 %x, i32 %y)
+  ret i8 %1
+}
+
+define i8 @scmp_2(i32 %x, i32 %y) {
+  ; X is within [4, +INF)
+  %cond1 = icmp sge i32 %x, 4
+  call void @llvm.assume(i1 %cond1)
+  ; Y is within [-INF, 4)
+  %cond2 = icmp slt i32 %y, 4
+  call void @llvm.assume(i1 %cond2)
+
+  %1 = call i8 @llvm.scmp(i32 %x, i32 %y)
+  ret i8 %1
+}
+
+; Negative test: ranges overlap
+define i8 @ucmp_3(i32 %x, i32 %y) {
+  ; X is within [4, +INF)
+  %cond1 = icmp uge i32 %x, 4
+  call void @llvm.assume(i1 %cond1)
+  ; Y is within [0, 6)
+  %cond2 = icmp ult i32 %y, 6
+  call void @llvm.assume(i1 %cond2)
+
+  %1 = call i8 @llvm.ucmp(i32 %x, i32 %y)
+  ret i8 %1
+}
+
+define i8 @scmp_3(i32 %x, i32 %y) {
+  ; X is within [2, +INF)
+  %cond1 = icmp sge i32 %x, 2
+  call void @llvm.assume(i1 %cond1)
+  ; Y is within [-INF, 4)
+  %cond2 = icmp slt i32 %y, 4
+  call void @llvm.assume(i1 %cond2)
+
+  %1 = call i8 @llvm.scmp(i32 %x, i32 %y)
+  ret i8 %1
+}
+
+; Negative test: mismatched signedness of range-establishing comparisons and
+;                of the intrinsic
+define i8 @ucmp_4(i32 %x, i32 %y) {
+  ; X is within [4, +INF)
+  %cond1 = icmp sge i32 %x, 4
+  call void @llvm.assume(i1 %cond1)
+  ; Y is within [0, 4)
+  %cond2 = icmp slt i32 %y, 4
+  call void @llvm.assume(i1 %cond2)
+
+  %1 = call i8 @llvm.ucmp(i32 %x, i32 %y)
+  ret i8 %1
+}
+
+define i8 @scmp_4(i32 %x, i32 %y) {
+  ; X is within [4, +INF)
+  %cond1 = icmp uge i32 %x, 4
+  call void @llvm.assume(i1 %cond1)
+  ; Y is within [0, 4)
+  %cond2 = icmp ult i32 %y, 4
+  call void @llvm.assume(i1 %cond2)
+
+  %1 = call i8 @llvm.scmp(i32 %x, i32 %y)
+  ret i8 %1
+}
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Poseydon42 wrote:

Yep, my bad. Fixed.

https://github.com/llvm/llvm-project/pull/97235