[llvm] Allow empty range attribute and add assert for full range (PR #100601)

[Andreas Jonson via llvm-commits]

https://github.com/andjo403 updated https://github.com/llvm/llvm-project/pull/100601

>From 7dc976da74a00e6526ea0b6e52775f6c12b73f91 Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Sun, 28 Jul 2024 17:51:27 +0200
Subject: [PATCH 1/2] Add pre-commit tests. NFC

---
 .../Transforms/Inline/ret_attr_align_and_noundef.ll   | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/llvm/test/Transforms/Inline/ret_attr_align_and_noundef.ll b/llvm/test/Transforms/Inline/ret_attr_align_and_noundef.ll
index f4cebf1fcb5da..dc685d2c4d136 100644
--- a/llvm/test/Transforms/Inline/ret_attr_align_and_noundef.ll
+++ b/llvm/test/Transforms/Inline/ret_attr_align_and_noundef.ll
@@ -410,3 +410,14 @@ define i8 @caller15_okay_intersect_ranges() {
   call void @use.val(i8 %r)
   ret i8 %r
 }
+
+define i8 @caller16_not_intersecting_ranges() {
+; CHECK-LABEL: define i8 @caller16_not_intersecting_ranges() {
+; CHECK-NEXT:    [[R_I:%.*]] = call range(i8 0, 0) i8 @val8()
+; CHECK-NEXT:    call void @use.val(i8 [[R_I]])
+; CHECK-NEXT:    ret i8 [[R_I]]
+;
+  %r = call range(i8 0, 5) i8 @callee15()
+  call void @use.val(i8 %r)
+  ret i8 %r
+}

>From 5565f4caa9e81b145e94386697c0fbd3b7f7a9d3 Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Wed, 7 Aug 2024 18:11:57 +0200
Subject: [PATCH 2/2] Allow empty range attribute and add assert for full range

---
 llvm/docs/LangRef.rst                                | 3 ++-
 llvm/lib/AsmParser/LLParser.cpp                      | 4 ++--
 llvm/lib/IR/Attributes.cpp                           | 4 ++++
 llvm/test/Assembler/range-attribute-invalid-range.ll | 4 ++--
 llvm/test/Bitcode/attributes.ll                      | 4 ++--
 5 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index b17e3c828ed3d..584084205268d 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1675,7 +1675,8 @@ Currently, only the following parameter attributes are defined:
     -  The pair ``a,b`` represents the range ``[a,b)``.
     -  Both ``a`` and ``b`` are constants.
     -  The range is allowed to wrap.
-    -  The range should not represent the full or empty set. That is, ``a!=b``.
+    -  The empty range is represented using ``0,0``.
+    -  Otherwise, ``a`` and ``b`` are not allowed to be equal.
     
     This attribute may only be applied to parameters or return values with integer 
     or vector of integer types.
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 9358f89e2bf9d..f41907f035125 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -3109,8 +3109,8 @@ bool LLParser::parseRangeAttr(AttrBuilder &B) {
   if (ParseAPSInt(BitWidth, Lower) ||
       parseToken(lltok::comma, "expected ','") || ParseAPSInt(BitWidth, Upper))
     return true;
-  if (Lower == Upper)
-    return tokError("the range should not represent the full or empty set!");
+  if (Lower == Upper && !Lower.isZero())
+    return tokError("the range represent the empty set but limits aren't 0!");
 
   if (parseToken(lltok::rparen, "expected ')'"))
     return true;
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index abd05e316bec1..fa124e46483dc 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -171,6 +171,7 @@ Attribute Attribute::get(LLVMContext &Context, Attribute::AttrKind Kind,
                          const ConstantRange &CR) {
   assert(Attribute::isConstantRangeAttrKind(Kind) &&
          "Not a ConstantRange attribute");
+  assert(!CR.isFullSet() && "ConstantRange attribute must not be full");
   LLVMContextImpl *pImpl = Context.pImpl;
   FoldingSetNodeID ID;
   ID.AddInteger(Kind);
@@ -2020,6 +2021,9 @@ AttrBuilder &AttrBuilder::addInAllocaAttr(Type *Ty) {
 
 AttrBuilder &AttrBuilder::addConstantRangeAttr(Attribute::AttrKind Kind,
                                                const ConstantRange &CR) {
+  if (CR.isFullSet())
+    return *this;
+
   return addAttribute(Attribute::get(Ctx, Kind, CR));
 }
 
diff --git a/llvm/test/Assembler/range-attribute-invalid-range.ll b/llvm/test/Assembler/range-attribute-invalid-range.ll
index cf6d3f0801838..1ddb6745e5dc2 100644
--- a/llvm/test/Assembler/range-attribute-invalid-range.ll
+++ b/llvm/test/Assembler/range-attribute-invalid-range.ll
@@ -1,6 +1,6 @@
 ; RUN: not llvm-as < %s -o /dev/null 2>&1 | FileCheck %s
 
-; CHECK: the range should not represent the full or empty set!
-define void @range_empty(i8 range(i8 0, 0) %a) {
+; CHECK: the range represent the empty set but limits aren't 0!
+define void @range_empty(i8 range(i8 1, 1) %a) {
   ret void
 }
diff --git a/llvm/test/Bitcode/attributes.ll b/llvm/test/Bitcode/attributes.ll
index f4dc9b9849827..c6d8fe1937644 100644
--- a/llvm/test/Bitcode/attributes.ll
+++ b/llvm/test/Bitcode/attributes.ll
@@ -531,8 +531,8 @@ define range(i32 -1, 42) i32 @range_attribute(<4 x i32> range(i32 -1, 42) %a) {
   ret i32 0
 }
 
-; CHECK: define range(i32 0, 42) i32 @range_attribute_same_range_other_bitwidth(i8 range(i8 0, 42) %a)
-define range(i32 0, 42) i32 @range_attribute_same_range_other_bitwidth(i8 range(i8 0, 42) %a) {
+; CHECK: define range(i32 0, 0) i32 @range_attribute_same_range_other_bitwidth(i8 range(i8 0, 42) %a)
+define range(i32 0, 0) i32 @range_attribute_same_range_other_bitwidth(i8 range(i8 0, 42) %a) {
   ret i32 0
 }