Revert "[vm] Arm Assembler simplify code for SubImmediateSetFlags"

dcharkes · commit-bot@chromium.org · commit 902e2b097b2d · 2020-02-13T10:25:07.000Z
This reverts commit be38459. Reason for revert: Comments in other pieces of the code state that kMinInt should be able to flow into SubImmediateSetFlags. Original change's description: > [vm] Arm Assembler simplify code for SubImmediateSetFlags > > See https://dart-review.googlesource.com/c/sdk/+/124136/9/runtime/vm/compiler/assembler/assembler_arm.cc#3203 > > Change-Id: I8d2a1bb781f22d6aae0e02eacf042a203a44790d > Cq-Include-Trybots: luci.dart.try:vm-ffi-android-debug-arm-try,vm-ffi-android-product-arm-try,vm-ffi-android-release-arm-try,vm-kernel-linux-release-simarm-try,vm-kernel-precomp-android-release-arm_x64-try,vm-kernel-precomp-bare-linux-release-simarm-try,vm-kernel-precomp-linux-debug-simarm_x64-try,vm-kernel-precomp-linux-release-simarm-try,vm-kernel-precomp-linux-release-simarm_x64-try > Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/134333 > Commit-Queue: Daco Harkes <dacoharkes@google.com> > Reviewed-by: Martin Kustermann <kustermann@google.com> TBR=kustermann@google.com,dacoharkes@google.com # Not skipping CQ checks because original CL landed > 1 day ago. Change-Id: Idb6ec6e55256c3a4894179a844d118a41378a074 Cq-Include-Trybots: luci.dart.try:vm-ffi-android-debug-arm-try, vm-ffi-android-product-arm-try, vm-ffi-android-release-arm-try, vm-kernel-linux-release-simarm-try, vm-kernel-precomp-android-release-arm_x64-try, vm-kernel-precomp-bare-linux-release-simarm-try, vm-kernel-precomp-linux-debug-simarm_x64-try, vm-kernel-precomp-linux-release-simarm-try, vm-kernel-precomp-linux-release-simarm_x64-try Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/135645 Reviewed-by: Daco Harkes <dacoharkes@google.com> Commit-Queue: Daco Harkes <dacoharkes@google.com>
diff --git a/runtime/vm/compiler/assembler/assembler_arm.cc b/runtime/vm/compiler/assembler/assembler_arm.cc
@@ -3164,16 +3164,34 @@ void Assembler::SubImmediate(Register rd,
                              Register rn,
                              int32_t value,
                              Condition cond) {
-  ASSERT(value != kMinInt32);  // Cannot be negated.
   AddImmediate(rd, rn, -value, cond);
 }
 
 void Assembler::SubImmediateSetFlags(Register rd,
                                      Register rn,
                                      int32_t value,
                                      Condition cond) {
-  ASSERT(value != kMinInt32);  // Cannot be negated.
-  AddImmediateSetFlags(rd, rn, -value, cond);
+  Operand o;
+  if (Operand::CanHold(value, &o)) {
+    // Handles value == kMinInt32.
+    subs(rd, rn, o, cond);
+  } else if (Operand::CanHold(-value, &o)) {
+    ASSERT(value != kMinInt32);  // Would cause erroneous overflow detection.
+    adds(rd, rn, o, cond);
+  } else {
+    ASSERT(rn != IP);
+    if (Operand::CanHold(~value, &o)) {
+      mvn(IP, o, cond);
+      subs(rd, rn, Operand(IP), cond);
+    } else if (Operand::CanHold(~(-value), &o)) {
+      ASSERT(value != kMinInt32);  // Would cause erroneous overflow detection.
+      mvn(IP, o, cond);
+      adds(rd, rn, Operand(IP), cond);
+    } else {
+      LoadDecodableImmediate(IP, value, cond);
+      subs(rd, rn, Operand(IP), cond);
+    }
+  }
 }
 
 void Assembler::AndImmediate(Register rd,
