[WebAssembly] Fold TargetGlobalAddress with added offset (#145829)

Previously we only folded TargetGlobalAddresses into the memarg if they
were on their own, so this patch supports folding TargetGlobalAddresses
that are added to some other offset.

Previously we weren't able to do this because we didn't have nuw on the
add, but we can now that getelementptr has nuw and is plumbed through to
the add in 0564d06.

Fixes #61930

Author: badumbatish

llvm/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp

@@ -343,17 +343,29 @@ bool WebAssemblyDAGToDAGISel::SelectAddrAddOperands(MVT OffsetType, SDValue N,
   if (N.getOpcode() == ISD::ADD && !N.getNode()->getFlags().hasNoUnsignedWrap())
     return false;
 
-  // Folds constants in an add into the offset.
   for (size_t i = 0; i < 2; ++i) {
     SDValue Op = N.getOperand(i);
     SDValue OtherOp = N.getOperand(i == 0 ? 1 : 0);
 
+    // Folds constants in an add into the offset.
     if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Op)) {
       Offset =
           CurDAG->getTargetConstant(CN->getZExtValue(), SDLoc(N), OffsetType);
       Addr = OtherOp;
       return true;
     }
+
+    // Fold target global addresses into the offset.
+    if (!TM.isPositionIndependent()) {
+      if (Op.getOpcode() == WebAssemblyISD::Wrapper)
+        Op = Op.getOperand(0);
+
+      if (Op.getOpcode() == ISD::TargetGlobalAddress) {
+        Addr = OtherOp;
+        Offset = Op;
+        return true;
+      }
+    }
   }
   return false;
 }

llvm/test/CodeGen/WebAssembly/eh-lsda.ll

@@ -66,9 +66,9 @@ try.cont:                                         ; preds = %entry, %catch.start
 
 ; CHECK-LABEL: test1:
 ; In static linking, we load GCC_except_table as a constant directly.
-; NOPIC:      i[[PTR]].const  $push[[CONTEXT:.*]]=, __wasm_lpad_context
+; NOPIC:      i[[PTR]].const  $push[[CONTEXT:.*]]=, {{[48]}}
 ; NOPIC-NEXT: i[[PTR]].const  $push[[EXCEPT_TABLE:.*]]=, GCC_except_table1
-; NOPIC-NEXT: i[[PTR]].store  {{[48]}}($pop[[CONTEXT]]), $pop[[EXCEPT_TABLE]]
+; NOPIC-NEXT: i[[PTR]].store  __wasm_lpad_context($pop[[CONTEXT]]), $pop[[EXCEPT_TABLE]]
 
 ; In case of PIC, we make GCC_except_table symbols a relative on based on
 ; __memory_base.

llvm/test/CodeGen/WebAssembly/exception-legacy.ll

@@ -34,7 +34,7 @@ define void @throw(ptr %p) {
 ; CHECK:       call      foo
 ; CHECK:     catch     $[[EXN:[0-9]+]]=, __cpp_exception
 ; CHECK:       global.set  __stack_pointer
-; CHECK:       i32.{{store|const}} {{.*}} __wasm_lpad_context
+; CHECK:       i32.store __wasm_lpad_context
 ; CHECK:       call       $drop=, _Unwind_CallPersonality, $[[EXN]]
 ; CHECK:       block
 ; CHECK:         br_if     0

llvm/test/CodeGen/WebAssembly/offset.ll

@@ -118,6 +118,16 @@ define i32 @load_i32_from_global_address() {
   ret i32 %t
 }
 
+define i32 @load_i32_global_with_folded_gep_offset_nonconst_nuw(i32 %idx) {
+; CHECK-LABEL: load_i32_global_with_folded_gep_offset_nonconst_nuw:
+; CHECK: i32.const $push0=, 2
+; CHECK: i32.shl $push1=, $0, $pop0
+; CHECK: i32.load $push2=, gv($pop1)
+  %s = getelementptr nuw i32, ptr @gv, i32 %idx
+  %t = load i32, ptr %s
+  ret i32 %t
+}
+
 ;===----------------------------------------------------------------------------
 ; Loads: 64-bit
 ;===----------------------------------------------------------------------------