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llvm-project/llvm/test/CodeGen/WebAssembly/wide-arithmetic.ll
Alex Crichton a415b7f86e
[WebAssembly] Add more lowerings for wide-arithmetic (#132430) 
This commit is the result of investigation and discussion on
WebAssembly/wide-arithmetic#6 where alternatives to the `i64.add128`
instruction were discussed but ultimately deferred to a future proposal.
In spite of this though I wanted to apply a few changes to the LLVM
backend here with `wide-arithmetic` enabled for a few minor changes:

* A lowering for the `ISD::UADDO` node is added which uses `add128`
where the upper bits of the two operands are constant zeros and the
result of the 128-bit addition is the result of the overflowing
addition.
* The high bits of a `I64_ADD128` node are now flagged as "known zero"
if the upper bits of the inputs are also zero, assisting this `UADDO`
lowering to ensure the backend knows that the carry result is a 1-bit
result.

A few tests were then added to showcase various lowerings for various
operations that can be done with wide-arithmetic. They don't all
optimize super well at this time but I wanted to add them as a reference
here regardless to have them on-hand for future evaluations if
necessary.
2025-03-31 11:36:32 -07:00

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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
; RUN: llc -mattr=+wide-arithmetic < %s | FileCheck %s
target triple = "wasm32-unknown-unknown"
define i128 @add_i128(i128 %a, i128 %b) {
; CHECK-LABEL: add_i128:
; CHECK: .functype add_i128 (i32, i64, i64, i64, i64) -> ()
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 1
; CHECK-NEXT: local.get 2
; CHECK-NEXT: local.get 3
; CHECK-NEXT: local.get 4
; CHECK-NEXT: i64.add128
; CHECK-NEXT: local.set 3
; CHECK-NEXT: local.set 4
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 3
; CHECK-NEXT: i64.store 8
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 4
; CHECK-NEXT: i64.store 0
; CHECK-NEXT: # fallthrough-return
%c = add i128 %a, %b
ret i128 %c
}
define i128 @sub_i128(i128 %a, i128 %b) {
; CHECK-LABEL: sub_i128:
; CHECK: .functype sub_i128 (i32, i64, i64, i64, i64) -> ()
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 1
; CHECK-NEXT: local.get 2
; CHECK-NEXT: local.get 3
; CHECK-NEXT: local.get 4
; CHECK-NEXT: i64.sub128
; CHECK-NEXT: local.set 3
; CHECK-NEXT: local.set 4
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 3
; CHECK-NEXT: i64.store 8
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 4
; CHECK-NEXT: i64.store 0
; CHECK-NEXT: # fallthrough-return
%c = sub i128 %a, %b
ret i128 %c
}
define i128 @mul_i128(i128 %a, i128 %b) {
; CHECK-LABEL: mul_i128:
; CHECK: .functype mul_i128 (i32, i64, i64, i64, i64) -> ()
; CHECK-NEXT: .local i64
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
; CHECK-NEXT: local.get 3
; CHECK-NEXT: i64.mul_wide_u
; CHECK-NEXT: local.set 5
; CHECK-NEXT: i64.store 0
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 5
; CHECK-NEXT: local.get 1
; CHECK-NEXT: local.get 4
; CHECK-NEXT: i64.mul
; CHECK-NEXT: i64.add
; CHECK-NEXT: local.get 2
; CHECK-NEXT: local.get 3
; CHECK-NEXT: i64.mul
; CHECK-NEXT: i64.add
; CHECK-NEXT: i64.store 8
; CHECK-NEXT: # fallthrough-return
%c = mul i128 %a, %b
ret i128 %c
}
define i128 @i64_mul_wide_s(i64 %a, i64 %b) {
; CHECK-LABEL: i64_mul_wide_s:
; CHECK: .functype i64_mul_wide_s (i32, i64, i64) -> ()
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 1
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.mul_wide_s
; CHECK-NEXT: local.set 1
; CHECK-NEXT: local.set 2
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
; CHECK-NEXT: i64.store 8
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.store 0
; CHECK-NEXT: # fallthrough-return
%a128 = sext i64 %a to i128
%b128 = sext i64 %b to i128
%c = mul i128 %a128, %b128
ret i128 %c
}
define i128 @i64_mul_wide_u(i64 %a, i64 %b) {
; CHECK-LABEL: i64_mul_wide_u:
; CHECK: .functype i64_mul_wide_u (i32, i64, i64) -> ()
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 1
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.mul_wide_u
; CHECK-NEXT: local.set 1
; CHECK-NEXT: local.set 2
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
; CHECK-NEXT: i64.store 8
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.store 0
; CHECK-NEXT: # fallthrough-return
%a128 = zext i64 %a to i128
%b128 = zext i64 %b to i128
%c = mul i128 %a128, %b128
ret i128 %c
}
define i64 @mul_i128_only_lo(i128 %a, i128 %b) {
; CHECK-LABEL: mul_i128_only_lo:
; CHECK: .functype mul_i128_only_lo (i64, i64, i64, i64) -> (i64)
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.mul
; CHECK-NEXT: # fallthrough-return
%c = mul i128 %a, %b
%d = trunc i128 %c to i64
ret i64 %d
}
declare { i64, i1 } @llvm.sadd.with.overflow.i64(i64, i64)
declare { i64, i1 } @llvm.uadd.with.overflow.i64(i64, i64)
; This is a codegen test to see the effect of overflowing adds on signed
; integers with wide-arithmetic enabled. At this time it doesn't actually
; generate anything differently than without wide-arithmetic but this has also
; been useful for evaluating the proposal.
define { i64, i1 } @add_wide_s(i64 %a, i64 %b) {
; CHECK-LABEL: add_wide_s:
; CHECK: .functype add_wide_s (i32, i64, i64) -> ()
; CHECK-NEXT: .local i64
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.add
; CHECK-NEXT: local.tee 3
; CHECK-NEXT: i64.store 0
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: i64.lt_s
; CHECK-NEXT: local.get 3
; CHECK-NEXT: local.get 1
; CHECK-NEXT: i64.lt_s
; CHECK-NEXT: i32.xor
; CHECK-NEXT: i32.store8 8
; CHECK-NEXT: # fallthrough-return
%pair = call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 %a, i64 %b)
ret { i64, i1 } %pair
}
define { i64, i1 } @add_wide_u(i64 %a, i64 %b) {
; CHECK-LABEL: add_wide_u:
; CHECK: .functype add_wide_u (i32, i64, i64) -> ()
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 1
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: i64.add128
; CHECK-NEXT: local.set 1
; CHECK-NEXT: local.set 2
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
; CHECK-NEXT: i64.store8 8
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.store 0
; CHECK-NEXT: # fallthrough-return
%pair = call { i64, i1 } @llvm.uadd.with.overflow.i64(i64 %a, i64 %b)
ret { i64, i1 } %pair
}
; This is a model of a hypothetical `i64.add_wide3_u` instruction using LLVM
; intrinsics. In theory this should optimize better (to the equivalent below)
; but it doesn't currently.
define { i64, i64 } @add_wide3_u_via_intrinsics(i64 %a, i64 %b, i64 %c) {
; CHECK-LABEL: add_wide3_u_via_intrinsics:
; CHECK: .functype add_wide3_u_via_intrinsics (i32, i64, i64, i64) -> ()
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: i64.add128
; CHECK-NEXT: local.set 2
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: local.get 3
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: i64.add128
; CHECK-NEXT: local.set 1
; CHECK-NEXT: i64.store 0
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: local.get 1
; CHECK-NEXT: i64.add
; CHECK-NEXT: i64.store 8
; CHECK-NEXT: # fallthrough-return
%pair = call { i64, i1 } @llvm.uadd.with.overflow.i64(i64 %a, i64 %b)
%t0 = extractvalue { i64, i1 } %pair, 0
%carry1 = extractvalue { i64, i1 } %pair, 1
%pair2 = call { i64, i1 } @llvm.uadd.with.overflow.i64(i64 %t0, i64 %c)
%ret1 = extractvalue { i64, i1 } %pair2, 0
%carry2 = extractvalue { i64, i1 } %pair2, 1
%carry1_64 = zext i1 %carry1 to i64
%carry2_64 = zext i1 %carry2 to i64
%ret2 = add i64 %carry1_64, %carry2_64
%r0 = insertvalue { i64, i64 } poison, i64 %ret1, 0
%r1 = insertvalue { i64, i64 } %r0, i64 %ret2, 1
ret { i64, i64 } %r1
}
; This is a model of a hypothetical `i64.add_wide3_u` instruction using 128-bit
; integer addition. This optimizes better than the above currently.
define { i64, i64 } @add_wide3_u_via_i128(i64 %a, i64 %b, i64 %c) {
; CHECK-LABEL: add_wide3_u_via_i128:
; CHECK: .functype add_wide3_u_via_i128 (i32, i64, i64, i64) -> ()
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 1
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: i64.add128
; CHECK-NEXT: local.get 3
; CHECK-NEXT: i64.const 0
; CHECK-NEXT: i64.add128
; CHECK-NEXT: local.set 1
; CHECK-NEXT: local.set 2
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
; CHECK-NEXT: i64.store 8
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 2
; CHECK-NEXT: i64.store 0
; CHECK-NEXT: # fallthrough-return
%a128 = zext i64 %a to i128
%b128 = zext i64 %b to i128
%c128 = zext i64 %c to i128
%t0 = add i128 %a128, %b128
%t1 = add i128 %t0, %c128
%result = trunc i128 %t1 to i64
%t2 = lshr i128 %t1, 64
%carry = trunc i128 %t2 to i64
%ret0 = insertvalue { i64, i64 } poison, i64 %result, 0
%ret1 = insertvalue { i64, i64 } %ret0, i64 %carry, 1
ret { i64, i64 } %ret1
}
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