[C API] Add usub_cond and usub_sat atomic ops to C API

These were added in the C++ API in llvm#105568
but were not exposed via the C API previously

Author: Benjins

Diff for: llvm/docs/ReleaseNotes.rst

@@ -204,6 +204,7 @@ Changes to the C API
   * ``LLVMGetNextDbgRecord``
   * ``LLVMGetPreviousDbgRecord``
 
+* Added ``LLVMAtomicRMWBinOpUSubCond`` and ``LLVMAtomicRMWBinOpUSubSat`` to ``LLVMAtomicRMWBinOp`` enum for AtomicRMW instructions.
 
 Changes to the CodeGen infrastructure
 -------------------------------------

Diff for: llvm/include/llvm-c/Core.h

@@ -395,6 +395,9 @@ typedef enum {
                                when incremented above input value */
   LLVMAtomicRMWBinOpUDecWrap, /**< Decrements the value, wrapping back to
                                the input value when decremented below zero */
+  LLVMAtomicRMWBinOpUSubCond, /**<Subtracts the value only if no unsigned
+                                 overflow */
+  LLVMAtomicRMWBinOpUSubSat,  /**<Subtracts the value, clamping to zero */
 } LLVMAtomicRMWBinOp;
 
 typedef enum {

Diff for: llvm/lib/IR/Core.cpp

@@ -3965,6 +3965,10 @@ static AtomicRMWInst::BinOp mapFromLLVMRMWBinOp(LLVMAtomicRMWBinOp BinOp) {
       return AtomicRMWInst::UIncWrap;
     case LLVMAtomicRMWBinOpUDecWrap:
       return AtomicRMWInst::UDecWrap;
+    case LLVMAtomicRMWBinOpUSubCond:
+      return AtomicRMWInst::USubCond;
+    case LLVMAtomicRMWBinOpUSubSat:
+      return AtomicRMWInst::USubSat;
   }
 
   llvm_unreachable("Invalid LLVMAtomicRMWBinOp value!");
@@ -3991,6 +3995,10 @@ static LLVMAtomicRMWBinOp mapToLLVMRMWBinOp(AtomicRMWInst::BinOp BinOp) {
       return LLVMAtomicRMWBinOpUIncWrap;
     case AtomicRMWInst::UDecWrap:
       return LLVMAtomicRMWBinOpUDecWrap;
+    case AtomicRMWInst::USubCond:
+      return LLVMAtomicRMWBinOpUSubCond;
+    case AtomicRMWInst::USubSat:
+      return LLVMAtomicRMWBinOpUSubSat;
     default: break;
   }
 

Diff for: llvm/test/Bindings/llvm-c/atomics.ll

@@ -58,6 +58,9 @@ define void @atomic_rmw_ops(ptr %p, i32 %i, float %f) {
   %a.uinc_wrap = atomicrmw uinc_wrap ptr %p, i32 %i acq_rel, align 8
   %a.udec_wrap = atomicrmw udec_wrap ptr %p, i32 %i acq_rel, align 8
 
+  %a.usub_sat  = atomicrmw usub_sat  ptr %p, i32 %i acq_rel, align 8
+  %a.usub_cond = atomicrmw usub_cond ptr %p, i32 %i acq_rel, align 8
+
   ret void
 }