[SelectionDAG] Drop unnecessary lower bound check in `lowerRangeToAssertZExt` (#196785)

Drop the `Lo.isMinValue()` check in `lowerRangeToAssertZExt`.
                                                                  
The check was introduced in 2bba779272a2 when the bit width was computed
via `logBase2(Hi)`, which required `Lo == 0` for correctness. It is no
longer needed since 9e04befb0979 when we switched to
`getUnsignedMax().getActiveBits()` for bit width.


The change in `DAGCombiner.cpp` is to prevent a regression in
`llvm/test/CodeGen/AMDGPU/llvm.amdgcn.wavefrontsize.ll`. I wasn't able
to construct an individual test for it.

---------

Co-authored-by: nikic <github@npopov.com>

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 3d65c82..14bf2b7 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -16213,6 +16213,10 @@
       AssertVT == cast<VTSDNode>(N0.getOperand(1))->getVT())
     return N0;
 
+  // fold (assert?ext c, vt) -> c
+  if (isa<ConstantSDNode>(N0))
+    return N0;
+
   if (N0.getOpcode() == ISD::TRUNCATE && N0.hasOneUse() &&
       N0.getOperand(0).getOpcode() == Opcode) {
     // We have an assert, truncate, assert sandwich. Make one stronger assert

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 68ae86d..5753d74 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -10852,10 +10852,6 @@
   if (!CR || CR->isFullSet() || CR->isEmptySet() || CR->isUpperWrapped())
     return Op;
 
-  APInt Lo = CR->getUnsignedMin();
-  if (!Lo.isMinValue())
-    return Op;
-
   APInt Hi = CR->getUnsignedMax();
   unsigned Bits = std::max(Hi.getActiveBits(),
                            static_cast<unsigned>(IntegerType::MIN_INT_BITS));

llvm/test/CodeGen/X86/call-range-attr.ll

diff --git a/llvm/test/CodeGen/X86/call-range-attr.ll b/llvm/test/CodeGen/X86/call-range-attr.ll
new file mode 100644
index 0000000..80e03e9
--- /dev/null
+++ b/llvm/test/CodeGen/X86/call-range-attr.ll
@@ -0,0 +1,73 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+
+declare i64 @returns_i64()
+
+define i64 @call_range_nonzero_lo() nounwind {
+; CHECK-LABEL: call_range_nonzero_lo:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    callq returns_i64@PLT
+; CHECK-NEXT:    andq $-8, %rax
+; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    retq
+  %v = call range(i64 1, 2305843009213693952) i64 @returns_i64()
+  %r = and i64 %v, 2305843009213693944
+  ret i64 %r
+}
+
+define i64 @call_range_zero_lo() nounwind {
+; CHECK-LABEL: call_range_zero_lo:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    callq returns_i64@PLT
+; CHECK-NEXT:    andl $-8, %eax
+; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    retq
+  %v = call range(i64 0, 256) i64 @returns_i64()
+  %r = and i64 %v, 248
+  ret i64 %r
+}
+
+define i64 @call_range_narrow() nounwind {
+; CHECK-LABEL: call_range_narrow:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    callq returns_i64@PLT
+; CHECK-NEXT:    andl $-8, %eax
+; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    retq
+  %v = call range(i64 100, 256) i64 @returns_i64()
+  %r = and i64 %v, 248
+  ret i64 %r
+}
+
+; Negative tests
+
+define i64 @call_no_range() nounwind {
+; CHECK-LABEL: call_no_range:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    callq returns_i64@PLT
+; CHECK-NEXT:    movabsq $2305843009213693944, %rcx # imm = 0x1FFFFFFFFFFFFFF8
+; CHECK-NEXT:    andq %rcx, %rax
+; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    retq
+  %v = call i64 @returns_i64()
+  %r = and i64 %v, 2305843009213693944
+  ret i64 %r
+}
+
+define i64 @call_wrapped_range() nounwind {
+; CHECK-LABEL: call_wrapped_range:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    callq returns_i64@PLT
+; CHECK-NEXT:    movabsq $2305843009213693944, %rcx # imm = 0x1FFFFFFFFFFFFFF8
+; CHECK-NEXT:    andq %rcx, %rax
+; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    retq
+  %v = call range(i64 -100, 100) i64 @returns_i64()
+  %r = and i64 %v, 2305843009213693944
+  ret i64 %r
+}